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Three currently accepted Sclerosperma species appear to produce four different pollen morphologies. Sclerosperma mannii and S. walkeri pollen share the same distinct reticulate sculpture, but S. profizianum produces three different pollen types (microreticulate, fossulate, and perforate). The pollen morphology suggests that S. mannii and S. walkeri are sister taxa of the same intrageneric lineage. The pollen diversity observed in S. profizianum suggests (a) this taxon is unique regarding its pollen diversity despite being a non-heterostylous plant or (b) that circumscription of S. profizianum as a species may well be in the need of redefinition.

The partially reticulate sculpture of Molaspora aspera sp. nov., a marsileaceous megaspore from a Cenomanian deposit in western France, distinguishes it from other species of Molaspora. An acrolamella entirely surrounds and obscures a small tetrad scar, a feature that has been demonstrated hitherto within members of the genus only in M. fibrosa. It was also encountered for the first time in M. lobata, with which the new species is associated in the same French mesofossil assemblage. The ultrastructure of the sporoderm of M. aspera is similar to that of M. lobata, but differs particularly in that the inner epispore is markedly thicker and may also contain numerous large, homogeneous spherules or, alternatively, holes of comparable dimensions and only a few small spherules. It is possible that these are a response to some hostile bacterial or other activity when the developing sporoderm was partially permeable. The cavity replacing part of the epispore in one of the specimens, and in the specimen of...

Here we describe the pollen morphology of 19 species of Alcantarea, none of them fully described before, to contribute to the infra-generic delimitation of the genus. Pollen grains are heteropolar, amb ellipsoidal (although spheroidal pollen occurs in Alcantarea aurantiaca, A. burle-marxii, A. glaziouana, A. nahoumii, A. roberto-kauskyi and A. trepida), monosulcate, sulcus with margin, reticulate ornamentation of the exine on the central area of pollen grain (except in A. imperialis, which display foveolate ornamentation) and apex of equatorial axe with different ornamentation from the central area of pollen grain (microreticulate calota or psilate-perforate calota). The genus is considered stenopalynous due to the similarity in the pollen morphology. The new pollen characters obtained here are useful in understanding the infra-generic palynotaxonomy of the genus confirming the relationship between species that have been grouped together based on vegetative evidence and/or relationships suggested ...

Pollen morphology of 24 Brazilian species of Codonanthe and Nematanthus (Gesneriaceae) was investigated by means of light microscopy, scanning and transmission electron microscopy, in search of new characters that might contribute to taxonomic characterisation of the genera. The pollen grains are tricolpate or tricolporate, semitectate, reticulate, with simplicolumellate muri, sometimes with microreticulum and perforations, or duplicolumellate muri ring-shaped around lumina. The species studied were grouped into five pollen types on the basis of aperture characteristics and details of surface ornamentation. Sub-types were defined with reference to presence or absence of microreticulum and perforations around the lumina. Based on analysis of the morphology and measurements of pollen grains, we verified a close relationship among the genera, but can nevertheless discriminate their species.

Microsporogenesis in Impatiens parviflora was studied with special attention to the mode of exine deposition and tapetum development. Our results are based on light, scanning electron and transmission electron microscopic observations of developing anthers of I. parviflora, from the microspore mother cell stage to anther dehiscence. In I. parviflora, the secretory tapetal cell layer is extended into the sporogenous tissue forming protrusions. The tapetal cytoplasm undergoes considerable changes during all stages of microsporogenesis such as fluctuations in volume densities of endoplasmic reticulum and plastids, occasional presence of two nuclei and the occurrence of a single very pronounced lipid droplet, which are indications that the tapetal cells are subject to cycles of different metabolic activity. Microsporogenesis in I. parviflora is simultaneous. Mature pollen is oblate, medium sized, 4-colpate, with a duplicolumellate reticulate sexine ornamentation. Anther dehiscence of I. parviflora in...

A study of the spores of 64 neotropical and palaeotropical taxa of the genus Blechnum was performed using scanning electron microscopy (SEM). Two basic types of perispores were recognised: perispore smooth or only slightly ornamented (laevigate, with micro-granules or micro-lamellae, venulose and rugulate), and perispore ornamented (rugate, low reticulate, cristatereticulate, orbiculate, and colliculate). SEM observations allow for distinguishing differences in the structure of perispores, but the character does not correlate with the ornamentation. The smooth exospore predominates among the studied species. Results suggest that perispore characters have important diagnostic value, since different combinations of ornamentation/ structure were found among the studied species. Moreover, when spore characters are considered together with other morphological traits of the sporophytes and the habit of plants, ornamentation of spores becomes a useful complementary feature at the specific level. The results are discussed in light of the recent systematic studies and emphasise that any eventual subdivision of the genus Blechnum must include characters of the sporophyte as well as spore features to ensure a more robust classification than the previously proposed. The spores also show a significant affinity between Blechnum and other genera of Blechnaceae, which was also suggested by recent phylogenetic studies., Laboratorio de Estudios de Anatomía Vegetal Evolutiva y Sistemática

An exhaustive search into the Cucurbitaceae pollen literature and own observations were used to arrive at a sharper delimitation of the pollen of subfamily Fevilleoideae against that of the other subfamily, the Cucurbitoideae. Pollen data of 125 out of the 128 genera including all 19 Fevilleoideae genera were available. In view of a broad overlap, pollen grain size is not a reliable criterium to separate both subfamilies. Striate and microstriate ornamentation appeared to be very useful in identifying cucurbitaceous plants as Fevilleoideae. The perforate-rugulate type of Alsomitra is unique in the family. Gerrardanthus cannot be indicated as a member of the Fevilleoideae with pollen features alone, its relatively large (micro)reticulate pollen being similar to that of several Cucurbitoideae. On the basis of outgroup comparison, either striate or perforate-rugulate might be considered as the plesiomorphic ornamentation state in the family Cucurbitaceae. The (micro)reticulate type occurring commonl...

A new genus, Zlatkocarpus gen. nov., is described from the Peruc Korycany Formation (Cenomanian) of the Bohemian Cretaceous Basin in the Czech Republic based on inflorescence axis, fruits and pollen. Two species are assigned to the new genus, Zlatkocarpus brnikianus and Z. pragensis. Zlatkocarpus has a compound inflorescence consisting of primary axes bearing semi-decussately arranged spikes. Each spike has helically arranged unicarpellate and unilocular fruits. Each fruit apparently contains a single, orthotropous seed. The stigma is indistinct and sessile at the apex. The fruit wall has distinct globular protrusions (probable resin bodies). The fruits are supported at the base by a small floral cup and a bract. Pollen grains adhering to stigmatic areas and also on other surfaces of the fossil are monocolpate with a long colpus and an open reticulum. The pollen is similar to dispersed pollen broadly referred to the extinct pollen genus Retimonocolpites, but none of dispersed pollen genera are su...

The massulae and pollen grains in pollinia of four palustrine South American species of Habenaria, H. bractescens, H. gourlieana, H. paucifolia and H. secunda were studied here for the first time using light, scanning, and transmission electronic microscopy. The pollinia have acalymmate, piriform or tabular massulae. Filiform elastoviscin threads are formed between the pollen grains of pollinia, allowing them to stick together. The pollen grains are inaperturate, grouped into calymmate tetrads, and have reticulate or reticulum-like, heterobrochate exine. Reticulate ornamentation consists of irregular, rounded, wide or narrow, continuous muri, while reticulum-like ornamentation is formed by discontinuous, partial muri, superficially smooth or with spherical micro-granules, intermingling with some isolated elements that can be interpreted as pila. The wall structure of individual pollen grains differs according to their position in the tetrads: outside walls develop complete exine and intine, with ...

Beschorneria yuccoides (Agavaceae) microspores are arranged mostly in planar tetrads. Later on, the pollen grains of the tetrad usually fall apart, but sometimes remain loosely connected by ektexine elements. The ektexine consists of a tectum, of short columellae, and of a thin, discontinuous foot layer. An endexine is absent. The bilayered intine is without any additional thickening that would usually indicate an aperture region. From this point of view the pollen grain might be considered as omniaperturate. The pollen ornamentation is reticulate with wide lumina and robust, smooth muri. The pollen grains show an indistinct sulcus characterised by a loose reticulate ornamentation. The sulcus is not exactly at the distal pole, but shifted towards the equator. No pollen tubes are formed regularly at the sulcus. Instead, pollen tubes are normally formed at the proximal pollen face. The proximal area, indicating a large germination field, is morphologically and functionally clearly an aperture (a ge...

The variability of ectexine sculpture in the pollen of Jaborosa runcinata (Solanaceae) was studied with light and scanning electron microscopy. Three main ectexine variants are recognized: incomplete reticulate, a combination of incomplete reticulate and gemmate‐granular, and gemmate‐granular. A range of transient conditions were also noted between the two extremes. Apertures vary from a basically triporate‐aspidate arrangement to pollen grains which appear to have a rudimentary colpus. The sculptural variability of the ectexine, and a tendency towards a colpus, in J. runcinata are interesting as intraspecific variation does not appear to be common within Solanaceae.

Pollen morphology and fertility in different populations of Pistacia atlantica from Algeria have been examined by light and scanning electron microscopy. Characteristics such as the shape and size of the pollen grains, the number of apertures, and the exine surface were recorded for each site for comparison. The pollen grains of Pistacia atlantica are consistently spheroidal to prolate spheroidal and pantoaperturate. The exine ornamentation is reticulate. Significant differences in pollen size and number of apertures were observed between the different sites. The fertility of pollen from different sites was estimated using the acetocarmine staining method and show that mean percentage of fertile pollen is high but varied among the sites with highest value (99.7%) at the Berriane site and lowest value (95.9%) at the Messaad site.

In order to provide additional data for the proposed subdivision of the palaeotropical genus Zehneria (Cucurbitaceae, tribe Benincaseae, subtribe Cucumerinae) by De Wilde and Duyfjes (2006) into five genera (Indomelothria, Neoachmandra, Scopellaria, Urceodiscus and Zehneria s.s.) pollen was examined using light and scanning electron microscopy for 18 Zehneria species including representatives of each of the proposed subdivisions, plus one species of the neotropical genus Melothria to which Zehneria once belonged. The pollen of Indomelothria, Scopellaria and Urceodiscus are described for the first time. Indomelothria, Neoachmandra and Zehneria s.s. have the same pollen type (3‐colporate, microreticulate to reticulate), which cannot be distinguished from that of Melothria. Scopellaria deviates by its irregularly striate‐reticulate ornamentation and short colpi, and Urceodiscus by its striate‐reticulate ornamentation. This result supports separation of Scopellaria and Urceodiscus as separate genera, but neit...

Pollen of Platanus was studied using light (LM) and electron microscopy (SEM and TEM). Overall, pollen is uniform in modern Platanus (small, tricolpate, prolate to spheroidal, reticulate, semitectate). A number of characters, however, display remarkable variability within a taxon and even a single anther (size; foveo‐reticulate, fine to coarse reticulate ornamentation). Platanus kerrii (subgenus Castaneophyllum) differs from the remaining species by its high and “folded” reticulum and possibly the smooth colpus membrane. Moreover, to our knowledge, pollen of the P. kerrii – type is not known from the fossil record. The exine in modern and fossil Platanaceae shows great structural similarity, but the thickness of the foot layer within the ectexine is less variable and normally smaller in modern taxa. Furthermore, in Early Cretaceous to Early Cainozoic Platanaceae a number of distinct pollen types occurred that are not known within the modern Platanus. Considering pollen of Platanaceae from the Early Cretac...

Pollen grains of 19 taxa of the genus Guettarda (Rubiaceae: Guettardeae) were studied using light microscopy, scanning electron microscopy (9 species), and fractured pollen grains (7 species). Most of the species have suboblate to oblate spheroidal, small to medium-sized grains with reticulate, microreticulate, perforate or foveolate exine. There is a great variability in the morphology of ectoapertures and endoapertures. Three pollen types are established, mainly based on differences in ectoapertures and sexine ornamentation.

Pollen morphology of 43 African species of the genus Spermacoce has been investigated by scanning electron and light microscopy. The genus is eurypalynous, which is reflected in the remarkable variation of almost all pollen characters. The average equatorial diameter (E) ranges from 15.8 w m to 115.5 w m. Grains are colporate or pororate. The number of apertures varies from 3 up to more than 25. The majority of species has apertures situated only at the equator (being zonoaperturate), but a few species have pantoaperturate grains. The endoaperture is generally an endocingulum, often with a secondary lolongate or lalongate thinning at the ectocolpus; endocolpi and endopores are also observed. The sexine is usually perforate, but eutectate, foveolate, and (micro)reticulate tecta were also found. Supratectal elements are present as granules, microspines or spines. The inner nexine surface is granular, often with irregular grooves (endocracks). Among native African species, nine pollen types are recognized ma...

Pollen of 34 accessions (23 species, one putative hybrid) of South Pacific and Hawaiian Cyrtandra was investigated by SEM. Most pollen grains are isopolar, 3-colpate, spheroidal in equatorial view, and circular in polar view. Only C. kamooloaensis (Hawaii) exhibits suboblate pollen grains. Average equatorial diameters range from 9 to 16mum. In general, colpi are long and tapering. Colpus membranes show granular elements which decrease in size from the equatorial to the polar regions. Most taxa exhibit a microreticulate mesocolpial exine pattern, in some cases with a tendency to reticulate or fossulate pattern. Lumina size varies within the mesocolpial region of single grains, average lumina diameter is either similar throughout grains or decreases towards the colpial borders or the apocolpial region. C. kamooloaensis exhibits the smallest lumina reported for Hawaiian Cyrtandra so far. In some species, distinct free-standing columellae are present. Except for a fine granular ornamentation of shallow groove...

Pollen grains of 24 species of Brunellia were examined with LM and SEM, in order to find additional taxonomic information for phylogenetic analysis. The pollen grains were found to be 3- colporate, tectate and to have variable exine pattern. Five types of exine pattern were observed: striate-reticulate (large lumina and high muri) to finely reticulate, modified reticulate (muri and lumina irregular in shape and at various levels), modified rugulate (irregular and with protruding tectal elements) and punctate (the lumina are smaller and rounded to slit-shaped). With reference to indication of taxonomic relationships the exine pattern is not informative at all; however it is useful, for defining taxonomic species as it is correlated to vegetative, inflorescence and fruit characteristics. It seems that the punctate type could be a plesiomorphic character while modified reticulate is a synapomorphy. Relationships in the pollen morphology of Brunellia and certain genera of Cunoniaceae are discussed. El polen d...

Pollen morphology of Euchaetis and Macrostylis , both members of the taxonomically problematic subtribe Diosminae (Rutaceae), was investigated by LM, SEM and TEM. Here we report on the taxonomic significance of pollen morphology based on a comparative study of 28 infrageneric taxa. Three pollen types were found, namely reticulate (common to both genera), perforate (in Euchaetis ) and striato-reticulate (in Macrostylis ). Pollen data provide evidence of relationships between the two genera as well as with other genera, and further support for the macromorphological evidence suggesting the generic re-classification of the Diosminae.

Although it is generally accepted that the tribe Genisteae has rather homogeneous pollen, we have found considerable variation in pollen size and morphology in Cytisus and related genera (Argyrocytisus and Chamaecytisus), which match taxonomic groups defined on morphological grounds. The results of Principal Component Analysis of pollen characteristics show the following: Cytisus Sect. Alburnoides is well-delimited, with the smallest pollen grains and the simplest pattern in the tectum, fossulate-perforate to perforate; No separation of C. villosus (Sect. Cytisus) from Sect. Alburnoides is observed; Cytisus Sect. Spartopsis, with the largest pollen grains and reticulate to reticulate-fossulate ornamentation, forms an isolated group; C. fontanesii (Sect. Heterocytisus) stands apart from other Cytisus species by its homogeneous ornamentation and the perforate instead of psilate-punctate margo. Thus, the pollen data supports its transfer to the separated genus Chronanthos; Pollen ornamentation and morphology...

Distinctive monocolpate and reticulate-acolumellate pollen grains with a coarse, loosely attached reticulum have long been known as a conspicuous element of many palynological assemblages from the Early and mid-Cretaceous. These grains are now described in situ in staminate structures and on the surface of pistillate organs from two Early Cretaceous (Barremian or Aptian) mesofloras from Portugal (Vale de Agua and Buarcos). Staminate organs include a staminate axis with spirally arranged stamens and many isolated stamens. Stamens consist of a short filament, a dithecate, tetrasporangiate anther, and a short apical extension of the connective. Anther dehiscence is extrorse by longitudinal slits and in situ pollen is monocolpate, semi-tectate with a coarse, loosely attached reticulum composed of narrow muri with a spiny ornamentation. The infratectal layer of the pollen wall is thin, granular, and lacking columellae; and the foot layer is distinct. The endexine is thin, except under the aperture where it is ...

The Aurantioideae is one of seven subfamilies of the Rutaceae consisting of two tribes, the Clauseneae, containing five genera, and the Citreae, with 28 genera. Each tribe contains three subtribes. The pollen morphology of the subfamily Aurantioideae is described and illustrated for the first time based on light and scanning electron microscopy. Five pollen types have been recognised in the subfamily, based mainly on aperture number and exine ornamentation. The pollen grains show a high degree of intergeneric variation. Pollen grains of Clauseneae are 3-colporate, microstriate or microstriato-reticulate, whereas pollen grains of Citreae are almost always 4/5 colporate with exines varying from microperforate to coarsely reticulate. Congruence between pollen types and the currently accepted classification is discussed, as well as the systematic implications of pollen morphology for the subfamily.

Studies in the pollen morphology of Argemone mexicana (a diploid species, 2n=28), A. ochroleuca (a tetraploid, 2n=56), the wild populations of which growing side by side, and of a triploid (2n=42) observed in the population of A. ochroleuca, have been carried out using light and scanning electron microscope. Pollen grains in both the species are 3 (-4)-zonocolpate with reticulate exine surface, and are distinguishable only on the basis of pollen size, the tetraploid species having larger pollen grains. In the triploid plant, a large number of grains deviates from the normal 3-zonocolpate condition showing a number of apertural types, such as 1-aperturate-operculate, 2-colpate, 3-syncolpate, 4-zonocolpate and spiraperturate. Besides, planaperturate 3-colpate-trilobed grains also occur. The triploid is also characterised by 'minigrains' (size 13-19 μm), a feature not observed in A. mexicana and A. ochroleuca. Since these species are reported to be genetically close, the occurrence of the triploids (forming ...

The pollen morphology of Diosma and Coleonema of the taxonomically problematic subtribe Diosminae (Rutaceae) was investigated to determine its taxonomic relevance. Pollen of 26 of the 28 species of Diosma and of each of the eight species of Coleonema was investigated by LM, SEM and TEM. In pollen of Diosma the exine sculpturing is uniform, and only one pollen type, reticulate, could be distinguished. In contrast, exine sculpturing shows interspecific variation in Coleonema and three distinct types, striate, reticulate and perforate, could be discerned. Species groupings indicated by the pollen types suggest possible relationships between species within Coleonema and with other genera that were not previously apparent. Pollen data support macromorphological evidence that suggests the generic re-classification of the Diosminae.

In a palynological study of the Amaranthaceae, a peculiar type of reticulate pollen was found that is characterized by the presence of a porate aperture in each of the meshes of the reticulum. Previously, this type of pollen has been described as “reticulate”;. However, closer investigations show that the reticulum in pollen of Amaranthaceae is composed of mesoporia and pores. Consequently, this kind of reticulum represents a fundamentally different type, and is not homologous to the well known examples of pollen grains with a true reticulum (e.g. in Bromeliaceae, Lamiaceae). Therefore, the term “metareticulate”; is proposed (i.e., pantoporate pollen with a reticulum‐like structure of mesoporia and pores). The new term allows to distinguish between metareticulate and truely reticulate pollen, what is important in phylogenetic studies. Metareticulate pollen occurs only within lineages characterized by pantoporate pollen, and is found to be derived from pantoporate pollen in a cladistic analysis. Apart from...

Pollen of all the southern African members of Canthium, Keetia and Psydrax was studied by means of LM, SEM and TEM. Palynologically these three genera can easily be distinguished from one another, exine structure and sculpturing being the most useful characters. The sexine is essentially perforate with short columellae not usually distinguishable in SEM in the Canthium type, coarsely reticulate with long columellae in the Keetia type and more finely reticulate with short columellae in the Psydrax type. Palynologically Canthium sensu stricto (used here to refer to the Canthium complex excluding Psydrax, Keetia and Pyrostria) is clearly distinct from Keetia and Psydrax, but similar to the other members of the Vanguerieae. This supports the proposed subdivision of Canthium sensu lato in southern Africa into these three genera. Differences amongst the various Canthium sensu stricto species suggest at least three different pollen sub‐types. Bridson's placement of C. inerme and C. suberosum in the subgenus Lyci...

The tribe Echieae of the subfamily Boragineae (Boraginaceae) is represented in southern Africa by the genera Lobostemon Lehm, and Echiostachys Levyns, endemic to the south‐western Cape region, and two species of Echium L., E. plantagineum L. and E. vulgare L., both introduced weeds of cultivation. Pollen of all these genera was studied and only one pollen type is recognized. Grains are tricolporate, heteropolar and triangular in equatorial view; ora more or less circular and situated towards the broader pole; tectum reticulate with densely spaced lumina; suprateetal nodules are situated at margins of lumina. The P/E ratio varies from 1.08 to 1.63. Genera of the Echieae are sometimes placed in the tribe Lithospermeae. A comparison of the pollen of the studied genera with that of Lithospermum, confirms that the tribe Echieae should be retained. Pollen of Lithospermum is 6–8‐zonocolporate, usually more or less isopolar and with colpi rhombic in outline. The presence of zygomorphic flowers and absence of calc...

A new angiosperm genus, Anacostia, with four species (A. marylandensis, A. virginiensis, A. portugallica, A. teixeirae) is described from Early Cretaceous floras in North America and Portugal. Anacostia comprises small, unilocular and one‐seeded fruiting units (each derived from a single carpel) with a sessile and indistinct stigmatic area. There are indications that a fleshy layer was originally present in the fruit wall. The seeds are anatropous, testai, and apparently derived from a bitegmic ovule. Pollen grains adhering to the stigmatic area and fruit wall are monoaperturate and trichotomocolpate or monocolpate. The pollen tectum is distinctly graded, reticulate to foveolate with the size of lumina decreasing towards the aperture and towards the proximal pole. The four species show substantial similarities in morphology, and in the anatomy of fruit, seed, and pollen, but can be distinguished by size and shape, as well as details of the fruit and seed wall. The Anacostia fruiting units are similar in s...

The pollen morphology of lianescent species of the genus Croton L. was analysed with regard to the size, number of apertures, shape and ornamentation of the exine. The pollen grains are apolar, atreme and spheroidal. They vary from medium to very large in size with croton- and reticulate pattern with supramural elements (clavae). The species are divided into two groups: (1) exine ornamentation with psilate sexine elements (C. grazielae) and (2) exine ornamentation with striate elements (remaining species). The latter group can be subdivided according to the formation or not of a croton-pattern by the sexine elements and by its ornamentation.

Pollen of the genus Passerina L. differs markedly from that of other southern African members of the Thymelaeaceae. Grains of most members of the Thymelaeaceae are characterised by a typical croton pattern, comprising rings of more or less trihedral sexine units mounted on an underlying reticulum of circular muri. In Passerina, however, the supratectal subunits are fused completely to form a continuous reticulum, which replaces the underlying reticulum. The reticulum in Passerina is therefore secondary in origin and not homologous with the basal reticulum of typical crotonoid grains in the family. The croton pattern has often been used as indication of a possible relationship between the Euphorbiaceae and Thymelaeaceae. Pollen of Passerina is adapted to anemophily. Grain sculpturing clearly demonstrates secondary derivation of a reticulate pattern from the typical croton pattern, through reduction, aggregation and fusion. Pollen of Passerina represents a climax of a continuum of variation in the ...

The pollen morphology of 31 species (50 accessions) of Ruellia L. is described and illustrated, based on examination with light, scanning and transmission electron microscopy. The pollen is spherical, coarsely reticulate (except for two species which are clavate), usually 3-porate, rarely 5-porate or 3-coIporate. Pollen is a good diagnostic character for Ruellia species. The pollen characters are discussed with regard to species relationships and functional significance.

As part of an extensive study of pollen of Euphorbiaceae that combines transmission electron microscopy with scanning electron microscopy, distinctive exines are reported and documented for certain Acalyphoideae. Cheilosa and Neoscortechinia, which comprise the tribe Cheiloseae, are the only Acalyphoideae with an echinate tectum, bur their apertures and exine structure do not support a relationship to Oldfieldioideae. In Ditaxis, one of the three mesocolpia is much smaller than the other two and the pollen can be easily distinguished from all other Euphorbiaceae. In SEM, the tectum of Pycnocoma appears almost complete, but in TEM the exine consists of irregular, mostly discrete rectal elements that narrow to points (=columellae) at the interface with the threadlike footlayer. The operculate grains of Alchornea and Boquillonia have exines with a poorly differentiated double layer of columellae in the mesocolpium, but nearer the endoaperture the lower tier becomes greatly elongated and appears to rest directly on the endexine. Plukenetia polyadenia has a complete tectum and a thick exine with a predominant infratectum of large, occasionally branched columellae that nearer the tectum are combined with densely spaced granules. Plukenetia penninervia has a reticulate tectum of crenate muri and short, sparse columellae. The pollen diversity in Acalyphoideae suggests that the subfamily, many tribes and even genera may not be monophyletic.

Pollen grains of Vitex (Labiatae) a large pantropical genus with a few temperate species, are examined by light microscopy, SEM and TEM. All grains are elliptic and tricolpate. However, exine surface sculpture varies between taxa. Two main morphological groups are recognized: the first is tectate simple-perforate to tectate perforate-fenestrate (with perforations anastomosing); the second tectate micro-reticulate/rugulate with micro-perforations in valleys between muri (the latter form is found in Madagascar taxa which have a long corolla tube). Pollen of the commonly cultivated Vitex negundo is unusual in having supra-rugulate, often collapsed grains. Polar and equatorial sizes are included and the possible taxonomic significance of the morphological differences discussed.

A blechnoid type of spore wall developed in Schizaea pectinata (L.) Sw. consisting of inner and outer exospore, inner and outer perispore. The inner exospore was initiated by the formation of electron dense lamellae from the surface of the plasma membrane around each member of the tetrad. Tetrads were enclosed within chambers in the plasmodial tapetum. The outer exospore constituted the bulk of the spore wall and accumulated, at first, in irregular patches on the inner exospore; its deposition involved the activity of the plasma membrane of the plasmodial tapetum. A reticulate pattern developed on the outer exospore as a result of a differential pattern of growth involving plasmodial tapetum activity. The heterogeneous inner perispore was firmly attached to the outer exospore and its deposition involved structures found in the sporangial loculus. The outer perispore was loosely attached to the inner perispore and its formation was associated with composite bodies, which differed from the structur...

Pollen morphology of nine species of the coryphoid genus Licuala Wurmb. (Palmae) is studied under light and scanning electron microscopes. The pollen grains have tectate exine with reticulate to microreticulate and punctate pattern. Exine stratification of similar type is also known in other coryphoid genera, e.g., Livistona, Sabal, Chamaerops, Corypha, Brahea and Washingtonia. Variations in the exine pattern in relation to the habitat of the plant is discussed.

The pollen morphology of the six Swedish Callitriche L. species was investigated using LM, SEM and TEM. The surface ornamentation is reticulate in C. stagnalis, C. platycarpa, C. cophocarpa and C. palustris with supratectal elements in the first three species. The ectexine is reduced in C. hamulata, occurring as scattered granules, but completely absent in C. hermaphroditica. None of the species has distinct apertures but C. cophocarpa and C. platycarpa both have leptomata. The ultrastructure of the pollen wall in C. palustris shows regions with lamellated footlayer and an endexine which may function as apertures. Pollen morphology is found to be related to pollination biology; species with leptomata sometimes being pollinated through ephydrophily and species with reduced exine being hyphydrophilous.

Pollen morphology of 33 Eurasiatic taxa of the genus Buxus was investigated by light and scanning electron microscope. The pollen is generally pantoporate. In comparison with the American and African sections of the genus, in which evolutionary lines from 3-colporatc to pantoporate conditions are found, the Eurasiatic species are more derived. A tendency to diminish pore size (O from 6.0 to 0.5–1.0 μm) as well as to increase number of apertures (from 12 up to 34) is correlated with geography, ranging from tropical SE Asia to the north and west parts of the area. Based on SEM details of exine 6 pollen types are described. Quantitative characters are listed, and LM and SEM illustrations are given. Pollen characters and evolutionary trends are discussed. Supposed evolutionary trends in pollen morphology of Eurasiatic Buxus are (primitive → derived character state): Pori round → irregularly shaped, distinct → indistinct margin, large → small, few → many. Exine reticulate → reticulate-verrucoid → verr...

Pollen of 20 species of Rondeletia, covering three subgenera and seven sections or “species groups” of the genus, was studied using light and scanning microscopy. Rondeletia, characterized by binucleate mature pollen grains like numerous other Rubiaceae, was found to be eurypalynous. The pollen is isopolar and small-sized (average equatorial diameters 11.4–22.8 μm) and 3-colporate (rarely 4-colporate). In equatorial view, the pollen grains are mostly ± spheroidal (rarely suboblate); in polar view (ambitus), they are mainly circular or semiangular (intersemiangular in one species only). Three different exine types are distinguishable: exine with 1) tectum minutely perforate, perforations usually isodiametric, 2) tectum with comparatively large, not isodiametric perforations or 3) coarsely reticulate; supratectal sculpturing elements are lacking; the width of the perforations and lumina is either equal or different at the apo- and mesocolpia; in a few species rod-like luminal processes are present....

The pollen morphology of 33 species (19 genera) of Bignoniaceae native to the south Brazilian Atlantic forest was examined using light- and scanning electron microscopy. The following pollen types were established: 1. inaperturate (Adenocalymma, Clytostoma and Pithecoctenium) 2. triaperturate (A) psilate (Jacaranda) (B) microreticulate (Arrabidaea, Fridericia, Lundia, Macfadyena, Melloa, Paragonia, Schlegelia and Tynnanthus) (C) reticulate (Cybistax, Pyrostegia and Tabebuia), 3. stephanocolpate (Amphilophium, Anemopaegma and Urbanolophium), 4. perisyncolpate (Mansoa).

Pollen of 108 species out of 18 genera (from all tribes of the Old World Gesneriaceae [subf. Cyrtandroideae]) was examined using light, scanning and transmission electron microscopy. The pollen grains are small sized, isopolar and 3-colpate or 3-colporate. In equatorial view they are mostly spheroidal (rarely suboblate or oblate), in polar view circular or subangular. The most variable character is the exine structure and -sculpture. The tectum is perforate, microreticulate, coarsely reticulate or rugulate. Further important characters of the tectum are (a) the presence or absence of conical supratectate sculptural elements, and (b) the width of lumina being either equal or exhibiting different at the apo- and mesocolpium. Ten exine types are distinguished. Some genera and species can be well referred to a special exine type, e.g., Aeschynanthus, Epithema, Stauranthera grandiflora; in other genera several exine types occur, e.g., in the large and heterogeneous genus Didymocarpus. The pollen morph...

Pollen grains of Ulex are isopolar, 3-zonocolporate with an ill-defined endoaperture, and tectateperforate to reticulate. The pollen grains have distinct internal folds due to the thickening of the endexine along the colpi. The general morphology does not vary substantially from one taxon to another, but the pollen wall structure is very variable. Three types have been recognized based on the stratification: Type I: a compact structure with an ill-developed infratectum mainly composed of granules; Type II: a transitional infratectal layer composed by granules and columellae; and finally, Type III: with a well differentiated columellar infratectum. These structural types correlate to a high degree with the different ploidy levels found in Ulex. Most of the diploid taxa have Type I, most of the tetraploids have Type II, and all of the hexaploids have Type III.

It has long been a matter of controversy whether to treat Cassine L. in southern Africa in a wide sense, or to recognize several segregate genera, such as Elaeodendron Jacq. f., Crocoxylon Eckl. & Zeyh., Lauridia Eckl. & Zeyh., Mystroxylon Eckl. & Zeyh. and Cassine s. str. The pollen morphology of the 14 southern African species currently included in Cassine s.l., as well as the three monotypic genera Allocassine N. Robson, Hartogiclla Codd, and Maurocenia Mill., has been studied by means of LM, SEM and TEM. Pollen grains in all species shed as monads, radially symmetrical, isopolar, tricolporate with colpus membranes conduplicate, tectate, subspheroidal, 14–30 μm in equatorial and 13–37 μm in polar diameter. On the basis of sexine sculpture three pollen types are recognized. Pollen type A (sexine reticulate) has been recorded in Maurocenia, Hartogiella, Cassine aethiopica, C. barbara, C. burkeana, C. eucleiformis, C. maritima, C. papillosa, C. parvifolia, and C. peragua; pollen type B (sexine fo...

The pollen of the bat- and moth-pollinated Browneopsis is spheroidal to oblate-spheroidal in shape, 3- or 4-colporate or 3- or 4-porate, with verrucate ornamentation. Three types are recognised: (1) 3-colporate with long, distinct colpi and verrucae interspersed with dense adpressed clavae or fine verrucae; (2) 3- or 4-colporate with short, indistinct colpi and irregularly shaped verrucae interspersed with a fine reticulum; (3) 4-porate with large scattered verrucae interspersed with adpressed clavae. There is a trend from colporate to porate pollen which is reflected in the petals which range from well-developed to rudimentary. The closely related bird-pollinated genus Brownea has distinctly different pollen which is prolate to prolate-spheroidal in shape, 3-colporate and with striate, striate-reticulate or reticulate ornamentation. The pollen morphology of the two genera is discussed in relation to pollination biology.

Small fruits with clumps of monocolpate, reticulate pollen grains of the Clavatipollenites type adhering to the stigmatic surface have been recovered from mid-Cretaceous (early Cenomanian) Potomac Group sediments of eastern North America. They provide the first megafossil evidence of this important early angiosperm pollen genus. The fruits are described as Couperites mauldinensis gen.et sp. nov. They are unicarpellate and unilocular containing a single, anatropous and pendulous seed. The fruit wall is thin with distinct, tubercular protrusions enclosing spherical resin bodies. The seed wall is apparently composed of two distinct tissues, indicating that the seed was probably derived from a bitegmic ovule. The outer tissue consists of one layer of cuboid palisade cells, the inner tissue consists of longitudinally elongated cells. Fruit and seed characters indicate that Couperites is more closely related to Chloranthaceae than to any other magnoliid family, and support the systematic affinity sugge...

The pollen morphology of 33 Malesian and Australian taxa of Polyscias is described, and the variation assessed by multivariate analysis. The analysis identified two main pollen types: (1) relatively small grains with a microreticulate tectum and lalongate ora (sect. Polyscias, Gelibia, Eupteron and six taxa not assignable to any of the sections as they are currently defined, (2) relatively large grains with a reticulate tectum, or which do not possess a tectum (previously unknown in the family), lalongate, lolongate or circular ora (sect. Kissodendron and Palmervandenbroekia). The systematic utility of palynologial data at various taxonomic levels within Polyscias is dicussed.

The present cytopalynological study relates to the pollen morphology of Arachis L., comprising diploid wild species, tetraploid species including the cultivated A. hypogaea (ground nut), diploid interspecific hybrids, and triploids and hexaploids of cultivars of A. hypogaea and of diploid wild species. In general, the pollen grains are 3-zonocolpate and reticulate/fossulate and trends in pollen variations have been noticed with regard to aperture and exine ornamentation. The size, shape and number of lumina (per unit area) as seen in SEM picture have provided the basic parameter for taxonomic differentiation of the species and even cultivars (in the case of A. hypogaea), and in the assessment of inheritance pattern in the hybrids.

Pollen grains of Shorea robusta Gaertn. (Dipterocarpaceae) were examined with light and scanning electron microscope. The pollen grains are tricolpate with reticulate sculpture with some of the muri discontinuous, giving a canaliculate appearance. The relation between pollen production and dispersal of Shorea robusta reveals that the huge numbers of pollen grains produced is associated with entomophily. The pollen grains have a poor dispersion power as indicated by substantial decline in percentage away from source trees. An extremely low percentage of sal (Shorea robusta) pollen deposited in ground soil within and outside and forest despite the high pollen production which may be attributed to microbial as well as chemical degradation. This information can be utilized for the precise evaluation of pollen diagram in terms of past vegetation and climate from tropical deciduous forests in the Indian sub-continent.

Pollen of 30 species representing the genera Koenigia, Persicaria and Aconogonon was examined by light microscopy and scanning electron microscopy. Pollen descriptions are given for each genus. Earlier palynological investigations of each genus are listed. Each of the genera is characterized by a particular surface structure (spinulose in Koenigia, semitectate reticulate in Persicaria, and with microspinules in Aconogonon), but the number and arrangement of the apertures varies considerably, showing interesting parallels in the three genera. All three genera follow the pollen evolutionary model called ‘successiformy’. A few evolutionary and phytogeographically interesting intermediates between these three genera are discussed.

Pollen grains of 36 Spanish species of Cistaceae belonging to the genera Cistus L., Helianthemum Miller, Halimium (Dunal) Spach, Fumana (Dunal) Spach and Tuberaria (Dunal) Spach have been examined. The pollen of Cistaceae varies from prolate to spheroidal, being tricolporate with long ectoapertures and circular endoapertures. Five types of exine have been recognized: reticulate-granular, rugulose, striate, retipilate and reticulate. Within Cistus there are species with rugulose, striate, retipilate and reticulate pollen, in Halimium only striate; in Tuberaria striate and reticulate; in Helianthemum rugulose and striate; in Fumana reticulate-granular and retipilate pollen. There is generally a good correlation between the taxonomic and the palynological data.