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SUMMARY As a sequel to biotaxonomic studies in Belgium, about 110 random population samples of Rumex acetosella L. s.l. from a large part of France were studied. Representatives of this polyploid complex were of common occurrence everywhere except in areas with a subsoil rich in lime. Angiocarpy is wide-spread, but gymnocarpy was only recorded from the French Alps. In contrast to the situation in Belgium, no correlation between the incidence of angiocarpy and a more fertile kind of soil could be established. Diploids (2n = 14) were found in the SE: Massif Central, Montagne Noire, Massif du Maure, and Massif du Mercantour in the Alpes Maritimes (altogether 36 populations); tetraploids (2n = 28, 23 populations recorded) are almost exclusively encountered in the Pyrenees and in the NE part of the Massif Central; and hexaploids (2n = 42, in 32 populations) appeared to be scattered over the remainder of the area studied, with a certain amount of sympatric overlap with the areas of the diploid and of the tetraploid chromosomal races in the Massif Central. In the zones of overlap an appreciable number of hybrids between 2n and 4n, and between 4n and 6n plants were encountered (in 11 populations). By far the large majority of the plants bear angiocarpous fruits irrespective of the level of ploidy, so that the alleged coupling between angiocarpy and diploidy (in the pertaining literature regarded as “R. angiocarpus Murb.”, with 2n = 14) must be rejected. In the Alpes Maritimes gymnocarpous diploids were found, which may be considered to represent a more primitive taxon among the aggregate. As far as can be ascertained, the distribution pattern of populations of the R. acetosella aggregate is, generally speaking, characteristic of a complex species differentiated during and after the last Ice Ages. In the discussion attention is paid to the possible causes underlying the differences in the distributional patterns (such as vegetative reproduction at higher ploidy levels). In order to obtain a more complete picture of the complex the investigations are being pursued. RESUME Comme suite aux recherches biotaxinomiques faites en Belgique, approximativement 110 echantillons des populations du Rumex acetosella L. s.l., provenantes d'une grande partie de la France, ont ete etudies. Representants de cet agglomerat polyploide etaient partout d'une presence frequente, a l'exception de regions avec un sous-sol calcifere. La forme angiocarpe se presente tres frequemment, tandis que la forme gymnocarpe ne se trouve que dans les Alpes Maritimes. Contraire a la situation en Belgique, la correlation entre l'incidence d'angiocarpie et un sol plus fertile n'a pas ete demontree. Des plantes diploides (2n = 14) ont ete trouvees dans le Sud-Est: le Massif Central, la Montagne Noire, le Massif du Maure et le Massif du Mercantour dans les Alpes Maritimes (36 populations au total). Des tetraploides (2n = 28, 23 populations) se trouvent presque exclusivement dans les Pyrenees et dans le Nord-Est du Massif Central. Des hexaploides (2n = 42, 32 populations) etaient repandues dans le reste de la region etudiee, avec des presences sympatriques dans le Massif Central ou les aires de la cytotype diploide, tetraploide et hexaploide se rencontrent. Dans cette region un grand nombre d'hybrides a ete trouve entre des plantes diploides et tetraploides ainsi qu'entre des plantes tetraploides et hexaploides (dans 11 populations au total). L'immense majorite des plantes a des fruits angiocarpes, independamment du niveau de ploidie, de sorte que la correlation du caractere angiocarpe avec le taxon diploide (considere dans la literature concernante comme Rumex angiocarpus Murbeck, 2n = 14) n'existe pas. Dans les Alpes Maritimes des diploides gymnocarpes ont ete trouves qui peuvent etre consideres comme un taxon primitif dans l'agglomerat en question. Selon la connaissance actuelle, la distribution de l'agglomerat polyploide du Rumex acetosella peut etre indiquee comme caracteristique de celle d'un complex qui s'est developpe pendant et apres les dernieres periodes glaciaires. Dans les discussions attention a ete pretee aux causes eventuelles de ces differences de distribution (p.e. l'augmentation vegetative aux niveaux de ploidie plus eleves). Afin d'obtenir une opinion plus complete sur ce complexe les recherches seront continuees.

SUMMARYThe study of meiosis in A. ampeloprasum in Israel showed that in subsp. ampeloprasum the chiasmata are localised proximally to the centromere, whereas they are terminal or subterminal in subsp. truncatum. It was found that localisation of chiasmata reduces multivalent formation in 4x, 5x and 6x plants of subsp. ampeloprasum.The distribution of ploidy levels of subsp. ampeloprasum (4x, 5x and 6x) and of subsp. truncatum (2x, 3x, 4x) in Israel is presented on maps.In both subspecies the tetraploid level is the most frequent. Hexaploids are rather common and probably arise from time to time from 4x in various localities. Pentaploids are fairly rare and possibly arise by hybridization between tetra- and hexaploids.Diploids are rare. They may have been replaced to a great extent by the apparently more vigorous and successful tetra- and triploids.Triploids seem to be maintained mainly by means of efficient vegetative reproduction; however, pollination of triploids by diploid pollen of tetraploids may occ...

The annual taxa of the western North American genus Stephanomeria (Compositae) provide excellent material for the comparative study of genetic differentiation and speciation in plants. They are a closely related assemblage, have broad and narrow distributions, occupy numerous habitats, and, in their center of variability in California, they are actively differentiating in response to sharp ecological gradients as well as the activities of man. They have long been known for their complex morphological intergradation (Ferris, 19660), which has stymied taxonomic efforts to separate the taxa. They exhibit a remarkable array of different evolutionary strategies involving changes in breeding system, polyploidy, hybridization, adaptation to particular substrates, and aggressive colonization of disturbed roadside habitats. As a result of the studies reported herein, the annual Stephanomerias are now known to include nine diploid (2n = 16) and two allotetraploid (2n = 32) taxa. Tetraploid chromosome numbers were first reported in Stephanomeria by Stebbins et al. (1953). They constitute both a polyploid complex and an homogamic complex in which the same divergent diploid species are connected by morphologically intermediate tetraploid and diploid species. Seven of the diploid taxa have a sporophytic selfincompatibility system and are consequently obligate outcrossers. The other two diploids and both tetraploids are selfcompatible and self-pollinating in the greenhouse. Their morphological, cyto

Diploid and tetraploid forms in sexual polyploid groups have been generally regarded as reproductively completely isolated from one another. Whether this is always the case was already questioned by Zohary (1956) and Stebbins and Zohary (1959). In the following work an attempt is made to examine the genetic relationships between diploid and tetraploid populations of the Orchard Grass, Dactylis glomerata L., in places where such populations come in contact in Israel. This paper reports on a study of the occurrence of natural triploids in contact areas and on the types of progeny such triploids produce under natural conditions. Previous studies (Zohary 1956, Stebbins and Zohary 1959) have established the polytypic group of Orchard Grass (Dactylis glomerata L.) as a large polyploid complex. This complex contains at least ten distinct diploid (2n = 14) subspecies as well as a large, sexual, tetraploid (2n = 28) superstructure. The diploid forms have each a restricted geographical distribution and they are widely separated from one another. Each diploid is characterized also by comparatively narrow and distinct range of variation. In contrast with the diploids, tetraploid Dactylis forms are continuously and widely spread over most of Europe, West Asia and North Africa. The tetraploid level is characterized by a large, continuous range of variation which covers most of the characters found in the various diploids. Cytogenetically all tetraploid forms are interfertile and show typical autopolyploid chromnosome behavior.

1. The cytological analysis of morphological variants inT. villosa Pers. revealed the existence of intra-specific polyploidy with distinct diploid and tetraploid races. 2. In diploids as well as in tetraploids, the meiosis was normal and 11 and 22 bivalents respectively were counted at metaphase-I. 3. The tetraploid individuals exhibited gigantism in most of the characters as compared to the diploid taxon. 4. It is suggested that the tetraploid race may be an allopolyploid.

Summary Results of a cytological survey of Hippocrepis comosa are reported and the geographical and ecological distribution of the three chromosome races, two of which occur in Britain, is described. Reasons for the restricted distribution of the diploid race are proposed and the probable post-glacial history of both British races is discussed. This intraspecific polyploidy is related to the evolution of a polyploid complex.

1. For 79 North American populations of the N. Hemisphere polyploid complexAchillea millefolium agg. (Asteraceae-Anthemideae) new tetraploid and hexaploid chromosome counts (n=18, 27 resp. 2 n=36, 54) are documented. 2. Together with literature references this adds to our knowledge of the distribution and affinities ofA. millefolium agg. cytotypes and races in North America. While 4 x types are widespread, autochthonous 6 x are found only in the W (California, and Oregon to southern Brit. Columbia), NW and NE. 3. More remarkable details concern relic 4 x races in coastal California, a subalpine 6 x ecotype in the N. Californian Coast Ranges, evidence for 4 x (apart from 6 x) in Alaska, and the sympatric occurrence (and hybridization?!) of introduced and evidently native 6 x on the Gaspe Peninsula. 4. The groups of disjunct 6 x races quite certainly have originated independently from each other, and — at least partly — directly from adjacent 4 x. Classification of all native North American 4 x as “A. lanulosaNutt.” and of all 6 x as “A. borealisBong.” is unnatural and impracticable.

The genus Geum of the family Rosaceae consists of about 56 species widely spread over the world except in the tropics. All species are perenniial herbs growing in more or less mesic conditions. More than fifteen years' study of this genus by the present author have shown that this genus is a polyploid complex of which the various species represent different stages of evolution, and show interesting relationships. In spite of great morphological differentiation on different polyploid levels the crossability between different species is surprisingly high, permitting cytogenetic analysis of 1lumerous interspecific hybrids. Geumt presents many interesting general problems concernin-g the role of geographical and ecological isolation as well as hybridization and polyploidy in the process of speciation. Some of the more interestinlg results of published (Gajewski, 1948, 1949, 1950, 1952, 1953, 1955, 1957) as well as unpublished results will be presented here.

Diploid (2n = 14) and tetraploid (2n = 28) entities in series Eubarbatae of the genus Avena have been found to be genetically closely linked and are regarded as a single polyploid complex. At both ploidy levels the various morphological types are interfertile. Diploids and tetraploids are largely sympatric in their distribution and converge considerably in their ranges of morphological variation. Contacts between diploids and tetraploids are common and blurred morphological boundaries characterize mixed populations.The possibility of gene flow between diploids and tetraploids has been indicated by the behavior of triploid F1 hybrids. Such hybrids have been found to be partially fertile. In their progeny a conspicuous restoration of fertility is apparent: numerous plants of the F2 generation have been stabilized around the tetraploid level, few around the diploid level. In contact areas, triploids can be regarded as efficient bridges of gene flow between the two ploidy levels.The range of variation found at the tetraploid level is fully explicable by the variation present in the diploid races. Tetraploids are therefore regarded to have had an inter-varietal origin, i.e. have evolved from a single genome. They apparently represent an extreme case of bivalentization, where a full shift from an autotetraploid to an allotetraploid meiotic behavior had occurred. Meiotic behavior of the F2 plants also indicate such origin.

In Bulinus as in other Planorbidae the basic haploid chromosome number is 18 and B. tropicus belongs to a group of diploid forms (2n=36) distributed predominately in southern Africa. B. truncates belongs to a group of tetraploid forms (2n=72) occurring mainly in northern Africa and extending northwards beyond the limit of the diploid forms. Hexaploid (2n= 108) and octoploid (2n= 144) populations occur in Ethiopia. Observations were made on snails belonging to this polyploid complex collected from 69 localities in Ethiopia. Chromosome numbers were determined in gonad tissue and in embryos. Morphological features studied are the shell (spire length, columella shape, umbilicus, costulation), radula (size of the first lateral tooth and the shape of its mesocone), copulatory organ (presence or absence) and egg size. Biochemical features investigated are the body-surface mucus, egg-proteins and esterase iso-enzymes. Certain diploid populations conform to B. natalensis and others to B. tropicus but these extremes are connected by intermediates preventing taxonomic subdivision and the entire diploid group is regarded as a northern part of the range of a B. natalensis/tropicus complex. Ethiopian tetraploid populations are identified as B. truncates because of similarity to Egyptian snails in morphology and egg-proteins and the susceptibility of some Ethiopian snails to infection with Egyptian Schistosoma haematobium. The shell spire is comparatively long in many hexaploid and octoploid populations, and distinctive egg-protein patterns are given by octoploids but these groups do not provide clear-cut taxonomic species. Hexaploids and octoploids are associated with streams at high altitudes while diploids and tetraploids occur in various habitats, most frequently at lower levels. The comparative rarity of the tetraploid B. truncates probably is one of the factors that have apparently prevented the establishment of truncates-borne strains of S. haematobium in Ethiopia, though present developments are likely to increase the abundance of tetraploid snails and provide opportunities for transmission of the parasite.

The taxonomy of the Trifolium longipes Nutt. complex (Leguminosae) in the western United States is reviewed. This polyploid complex consists of diploid, tetraploid, and hexaploid races having a base number of x = 8. For the most part, each race occupies a distinct geographical area. Keys to the three species recognized in this study and to the 11 subspecies of T. longipes in the restricted sense are provided. For each taxon a description and synonymy are given. Maps of the chromosome races and taxonomic entities are appended.

The wild tuber-bearing species of Solanum (Sect. Tuberarium) have long been recognized as a useful group for evolutionary and genetic studies (cf. Howard, 1961; Magoon et al., 1962; Dodds and Paxman, 1962; Hougas and Peloquin, 1960). The diversity of species and infraspecific taxa (Correll, 1962; Hawkes, 1963; Ochoa, 1962), together with the ease of seed and tuber propagation, makes this polyploid complex especially suitable for field and greenhouse investigations of experimental hybridizations between races and species. It is thus not surprising that much is known about the variability and crossability of wild and cultivated potatoes when grown under controlled conditions (Hawkes, 1958; Simmonds, 1964). In contrast, very few studies have concerned themselves with the dynamics of wild or cultivated potato populations in their native Mexican or Andean habitats. The investigations by Correll (1952) on the environmental-latitudinal modifications of S. demissum phenotypes and those of Hawkes (1962a) on introgression in S. chacoense and S. microdontum are of interest here, though neither study employed population concepts based upon mass sampling techniques (Anderson, 1949). Similarly, the experimental synthesis of S. X juzepczukii and S. x curtilobum from S. acaule and diploid and tetraploid clones of S. tuberosum (Hawkes, 1962b), while a milestone in potato systematics, nonetheless sheds little light on the true extent of morphological intergradation that occurs between these taxa in nature. One purpose of the present study is to explore the value of mass collection techniques and variability analyses in understanding the dynamics of natural hybrid potato populations. A series of small and local hybrid potato populations, sampled in Central Mexico during the summer of 1962, 1963, and 1965, will thus be analyzed following methods outlined by Anderson (1949). A second objective is to compare the results obtained from studies of native Mexican potato populations with those obtained from the analysis of plants cultivated under uniform field conditions at the University of Wisconsin Experimental Farm at Sturgeon Bay, Wisconsin. In this way both genetic and phenotypic variation will be compared and the responses of hybridizing plants to differing environmental conditions will be analyzed. The weedy Mexican potato, Solanum X edinense Berthault, is particularly wellsuited for these investigations as its partial sterility and pentaploid chromosome number (2n = 60) offer virtually indisputable proof of its hybrid origin (Hawkes, 1944, 1963). However, its postulated origin from a cross of S. tuberosum L. (Group Andigena, 2n = 48) with S. demissum Lindl. (2n = 72), as suggested by Hawkes (1944, 1966), has not hitherto been supported by comparative morphological studies.

Bivalent pairing in the tetraploid oat A. barbata, the main tetraploid form of A. strigosa polyploid complex, was found to be determined by a single recessive gene in quadriplex condition. This gene segregated in tetrasomic fashion in the A. barbata × A. strigosa autopolyploid, which indicates conspicuously autopolyploid origin of A. barbata and close relationships between the two chromosome sets of this oat, and the chromosomes of the diploid oat A. strigosa. It was speculated that the gene affecting bivalent pairing in A. barbata was evolved already at the diploid level in one of the A. strigosa races and had been recovered in quadriplex state following polyploidization of an intervarietal A. strigosa hybrid.

Thermeda australis (R.Br.) Stapf is a polyploid complex based on n = 10, and diploid, triploid, tetraploid, pentaploid, and hexaploid individuals have been found. Over 98 per cent. of more than 800 individuals examined were either diploid or tetraploid. Some 300 populations, from localities on the Australian mainland below the Tropic of Capricorn, were characterized by their chromosome number and a very clear pattern of distribution was found. Diploid populations occur exclusively on the Eastern Highlands and slopes in southern Victoria and in Tasmania; elsewhere tetraploid populations occur across to Western Australia. Triploid, pentaploid, and hexaploid plants are found as individuals in populations of another chromosome number. The cytological evidence shows a very close relationship to exist between the constituent genomes of the polyploids. The significance of the distribution of the chromosome races, the effects of polyploidy, and the implications of this pattern for further studies on the native flora are discussed.

Taxonomic work on Tripsacuml has indicated that T. dactyloides is a very complex species. It is composed of at least five different entities, one of which grows in an isolated area in westerni Texas and has been recognized taxonomically as T. dactyloides var. occidentale (loc. cit). Aside from this variety, T. dactyloides extends from central Texas and northern Kansas eastward to Connecticut and Florida (Map 1). Cytologically, T. dactyloides is a polyploid complex and has some races with 18 pairs of chromosomes and others with 36. The cytological work reported below extends the known range of one diploid race into Missouri and Arkansas and suggests that T. dactyloides may be exclusively tetraploid along the eastern seaboard.