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Necessity of a thorough study of hybridization, following the breakdown of reproductive isolating mechanisms between naturally occurring populations, has been felt by biologists in general and ichthyologists in particular. In this connection a formula for ‘hybrid index’ developed mainly by Hubbs & Kuronuma (1942) and Hubbs, Hubbs & Johnson (1943) has widely been in use, to test the assumption of hybridity and to study the mode of inheritance. Misra, Bateson & Keenleyside (1970) gave statistical methods of analysing hybrid indices estimated for characters of the ‘continuous’ type, and also provided a numerical example. Recently Misra (1971) gave a method of doing similar analysis for hybrid indices estimated for meristic characters, but no example was provided, as data were not available to him. This paper presents a study of hybridization in the sunfishes (genus Lepomis) of Pinehurst Lake, Ontario, Canada, based on the number of scales below the lateral line; the primary purpose of the study is to show the complete computational procedure involved in the application of the method of Misra (1971), so that those users of the method who are mainly interested in the applied aspects of the method, can bypass the mathematics easily. [ABSTRACT FROM AUTHOR]

The distribution of male and female florets in heads of monoecious populations is represented by a curve joining points on a graph of percentage of female florets against rank in the same percentage. Comparison of curves for samples from different origins in Cotula minor and C. atrata subsp. atrata shows that sex expression is not greatly influenced by macro-environmental differences. Much of the total intra-population variation in sex expression appears in the heads collected at one time from a single plant. The rank-frequency curves show marked differences between species in the percentages of male and female florets. The average percentage of female florets in seventeen monoecious species is negatively correlated with the floret length, a measure of adaptation to out breeding. In three species, the seed set and subsequent germination percentages are slightly lower after self-pollination than after cross-pollination. Self-fertilization probably occurs in varying degrees in the monoecious species. Monoecy has arisen independently in sections Leptinella and Strongylosperma. [ABSTRACT FROM AUTHOR]

A short review is given of the literature on sterile breeding of higher plants. A simple rearing apparatus is described. Instructions are given for its use with special regard as to the cultivation of endospermless wheat, 56 seedlings of which can be cultured in each unit. [ABSTRACT FROM AUTHOR]

Heteranthelium is a monotypic genus in the tribe Triticeae represented by an annual diploid species, H. piliferum. The spike of this species is quite different from other members of the tribe. In an attempt to elucidate the genetic relationships to other genera of the tribe, H. piliferum was crossed with various species of Aegilops, Agropyron, Eremopyrum, Henrardia and Hordeum. From these crosses F1 hybrids of (1) Heteranthelium piliferum (2x) × Eremopyrum bonaepartis (2x) and (2) Heteranthelium piliferum × Hordeum depressum (4x) were produced. At the same time F1 hybrids of (3) Eremopyrum bonaepartis × Hordeum depressum was also obtained. The hybrid under (1) showed subnormal growth and the shape of the spikes was of Eremopyrum-type, while the spikelets were intermediate. Growth of the hybrid under (2) was vigorous and the spike morphology was intermediate between the parents. A solitary spikelet with two glumes and a single spikelet at each rachis node like the Heteranthelium parent was observed but no rudimental spikelets which are the characteristic of Heteranthelium were found. Growth of the hybrid under (3) was very vigorous and the shape of the spikes was of Hordeum type. However, floral construction at each rachis node was very complicated. Rachis nodes with three glumes and a single spikelet were the most common. Sterility of all three combinations was complete. Average chromosome pairing per cell of the F1 hybrids was in (1) 0.04 bivalents and 13.93 univalents, in (2) 0.00 trivalents, 5.06 bivalents and 10.88 univalents, and in (3) 0.00 quadrivalents, 0.01 trivalents, 5.50 bivalents and 9.97 univalents. Judging from the chromosome pairing in (1), (2) and (3), a high bivalent formation in (2) and (3) is attributable to autosynthesis of chromosomes derived from the Hordeum parent. It is concluded that there is no homology among the genomes of those three species. Considering morphological features, geographical distribution, intergeneric cross-ability and genetic relationships of Heteranthelium piliferum, it is concluded that the monotypic genus Heteranthelium is a distinct entity in the tribe Triticeae. This taxon has evolved as an annual during the process of adaptation to rather dry habitats of the Mediterranean climatic regions in the course of generic differentiation of the tribe. [ABSTRACT FROM AUTHOR]

Experiments with two other varieties of wheat confirmed the earlier observation (Asana et al. 1958) that reduction in leaf and stem surface, due to drought after ear emergence, did not affect grain development as long as the ear remained green. Drought reduced the grain number of the two varieties to the same extent. The 1000-grain weight of Pb C 281, and therefore the yield, exceeded that of the N. P. 720, under normal water supply and drought, only during the last week of the maturation period when the ear of the former was relatively greener and the maturation period when the ear of the former was relatively greener and the leaves and stems of both were yellow. It is pointed out that the little effect of drought on grain development during the early stages cannot be accounted for by increase photosynthetic activity due to 'hardening' or by increase in supply of catabolic products from leaves. Under drought the water content of the ear was little affected but the grain number was reduced; this anomaly may perhaps be due to failure to detect minute changes in the water content of flowers. The bearing of these observations on breeding varieties for unirrigated conditions is discussed. [ABSTRACT FROM AUTHOR]

The article discusses a rapid technique for the examination of large numbers of ryegrass samples for blind seed disease. The breeding of cultivars of Lolium perenne L. resistant to blind seed disease, Gloeotinia temulenta currently in progress at Loughgall, involves the testing, for disease reaction, of large numbers of progeny plants. When a simple and reliable field technique for artificial infection was developed, the rapid and accurate assessment of infection in individual plant seed-harvests, on a large scale, posed a formidable problem. A technique, which seemed applicable to large numbers of samples, was that used by Fischer, to detect the level of infection on ryegrass heads, and modified by Hardison to estimate infection in crop seed samples. This involved centrifuging, and haemocytometer counts of the conidia. Rose heated seeds in water before making haemocytometer counts but found the errors to be too great.

Within the pointer breed of dog two strains have been developed by selective mating and line breeding. The goal is that of producing behaviorally distinct stable and unstable (nervous) strains to measure hereditary effects including dominance and sex Unkage, if present, Some behavioral difference emerged early. Measures of operant conditioning and other behavioral tests have little overlap. We conclude that genetic controls are important for behavioral research, even within a single breed, and that temperamental variables have strong genetic factors as well ss environmental ones. [ABSTRACT FROM AUTHOR]

Sunfish specimens (genus Lepomis) collected from Pinehurst Lake, Ontario, Canada, were identified as bluegill (L. macrochirus), pumpkinseed (L. gibbosus) and their hybrids. Hybridization was studied on the basis of the constants of cross-sectional allometry as, to the best of our knowledge, no attempt has ever been made to study hybridization quantitatively from the relative growth aspect. Two sets of data—one on the pair Y1/X (head length/standard length) and the other on the pair Y2/X (body depth/standard length)—were analysed, with the following objectives: (i) A statistical method of analysing hybrid index based on cross-sectional allometry was first presented and then Y1/X-data analysed by this method, and (ii) data Y2/X were analysed to show that in some particular situations analysis for hybridization by methods other than the hybrid index approach may be more appropriate. Results of the analyses were discussed. [ABSTRACT FROM AUTHOR]

The article reports on polymorphism and natural selection. It states that there was a small outbreak in the literature which appeared in "American Naturalist," occasioned by the criticism of Oxford zoologists P. M. Sheppard and A. J. Cain as well as the claim made by T. Dobzhansky in his book "Genetics and the Origin of Species." The author mentions the three points made by Sheppard and Cain. One of which is that while admitting that if polymorphism within a breeding community increases the efficiency of the development of the resources of the environment then polymorphic organisms could be considered as better adapted than monomorphic ones.

The article offers information on a study conducted in February 1928, on the annual physico-chemical cycle occurring in the waters of six ponds in the district of Farnham Royal in Buckinghamshire, England, with a view to know the mosquito ecology. It states that the ponds selected include the Tithe Farm Fond, a constantly running stream in a public pasture, and the Elm Cottage Pond in a private garden. It offers information on various data such as the temperature, the hydrogen-ion concentration, the ammonia nitrogen content and the dissolved oxygen contents collected from the water of the ponds. It discusses the physico-chemical factors as possible determinants of mosquito breeding, and mentions that the data collected show that certain mosquitoes exhibit preferences for particular ponds.

Five classes of sex expression are distinguished in Cotula on the basis of the degree of separation of male and female gametes on different flowers and plants. These classes are divided into sexually monomorphic and dimorphic systems. The order--monocliny, gynomonoecy, monoecy, subdioecy, dioecy--places the five classes in a linear sequence of increasing dependence for fertilization on the transfer of pollen between flowers and plants. Four of the five major taxonomic groups in Cotula and five species have more than one class of sex expression. The four monoecious and gynomonoecious species tested are self-compatible. The morphology of hermaphrodite, male and female florets are compared. Seven additional characters are associated with sex expression in New Zealand species. In general, the extent of protogyny, brightness of flowers, degree of retraction of stigmas and anthers, floret length, head diameter, peduncle length and the number of pollen grains increase from gynomonoecious through monoecious to dimorphic (dioecious or subdioecious) populations. But within each kind of sex expression there is considerable variation in these ancillary characters. A MAS (measurements associated with sex expression) index is calculated from the four quantitative characters for each New Zealand species (or part-species where there are two kinds of sex expression in a species). The MAS index reflects the expenditure of energy on adaptations to cross-pollination and provides an approximate measure of the relative frequency of outbreeding. The MAS indices of the species and part-species indicate a continuous array in the expression of adaptations to cross-pollination and the frequency of outbreeding. The different kinds of sex expression occupy characteristic but overlapping segments of this array and ought to be considered as convenient classes which only specify the breeding system approximately. [ABSTRACT FROM AUTHOR]

Open-pollinated seedling progenies of Eucalyptus obliqua grown in a uniform environment showed evidence of genetic variation among geographically different localities and among parent trees within localities. Locality variation did not appear habitat-correlated, so no predictor of a superior locality for tree-improvement purposes could be suggested, other than appearance of the trees; breeding strategy should include tree selection within localities. Several superior localities were indicated consistently but many showed marked fluctuations, suggesting the need for caution in interpreting seedling data. [ABSTRACT FROM AUTHOR]

The Rodentia exhibit a variety of reproductive patterns; some species show a continuous reproductive activity while the others exhibit a regular periodicity. Cyclical reproductive phenomena are generally characteristic of mammals living in temperate and subarctic regions. In some of these the cold winter months are passed in a torpid state during which the reproductive activity ceases. Such extreme environmental variations do not occur in the tropical and subtropical regions, except under certain xerotic conditions where aestivation may occur similarly associated with cessation of breeding.

Spray applications of 1000 mg/l (2‐chloroethyl)phosphonic acid (CEPA) five times, at weekly intervals, during November and early December induced heavy flowering in ringed and nonringed juvenile mango seedlings. The treated plants produced flower buds which opened by the end of December, while the control and ringed seedlings produced only a new flush of vegetative growth. The results show that CEPA could be profitably used for early evaluation of hybrid seedlings in mango breeding programme. [ABSTRACT FROM AUTHOR]