Advances in Genetics, vol. IX. by M. DemerecReview by: H. L. K. WhitehouseNew Phytologist, Vol. 57, No. 3 (Dec., 1958), pp. 406-407Published by: Wiley on behalf of the New Phytologist TrustStable URL: http://www.jstor.org/stable/2429750 .

Accessed: 12/06/2014 17:38

Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at .http://www.jstor.org/page/info/about/policies/terms.jsp

.JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact support@jstor.org.

.

Wiley and New Phytologist Trust are collaborating with JSTOR to digitize, preserve and extend access to NewPhytologist.

http://www.jstor.org

This content downloaded from 62.122.73.17 on Thu, 12 Jun 2014 17:38:46 PMAll use subject to JSTOR Terms and Conditions

406 Reviews scientists, such as ecologists, plant pathologists, agriculturalists, entomologists and foresters, and an even larger field of amateur botanists drawn from all ranks of society who cultivate an interest, more or less scientific, horticultural or aesthetic, in our native plants.

All these groups acknowledge readily their indebtedness to the authors of the Flora of the British Isles, our one modern and authoritative Flora. They will all unquestionably welcome the publication by the Cambridge University Press of the illustrations to that Flora of which the first 552 species now appear in a single extremely well-produced and very inexpensive volume. The most substantial basis for such a general welcome lies in the authority behind each illustra- tion. Each figure corresponds to a taxonomic entity described in the New Flora and illustrates a plant chosen by the authors of that Flora as representative of a species they have described. This conveys a validity hardly to be achieved in any other way: moreover the original plants from which the drawings were made are all preserved for reference in the University Herbarium at Leicester.

The work of taxonomic specialists compels them to give care to the recognition of many points of detail in floral morphology and structures, and some published floral illustrations con- centrate successfully upon these. Most of this detail is, however, already conveyed in the text of the Flora, and to the very numerous other users of the illustrations these details are of less significance than a faithful general impression of the living plant, associated with true and clear representation of the most evident features of leaf, flower and fruit shape and organization. It is no doubt this that fortunately persuaded the authors and the Cambridge Press to engage the services of Miss Roles and to secure that she should draw exclusively from living specimens. It is a delight to those whose concern is with plants as they grow to recognize the impressionistic but nevertheless faithful manner in which Miss Roles has caught the characteristic habit of most of her subjects: their delicacy, robustness, flaccidity and even the general texture of foliage and stems are presented with great realism. How welcome it is not to smell the her- barium corpses as one looks at these pictures.

Despite this general method of treatment there has been a reasonable illustration of those details which are of outstanding importance in the differentiation of related species. Thus we find beside the picture of the whole plant, drawings of the inflorescence, single flower, fruit and often of the seed, and it is satisfactory that scales of size are given alongside all these drawings. The arrangement of eight species per double page is one which will facilitate easy comparison, an advantage one can appreciate for instance by referring to the pages illustrating species of the genera Chenopodium, Trifolium and Papaver.

This volume seems to me to be a very successful attempt to retain the considerable virtues of the drawings by Fitch (that illustrated the old 'Bentham and Hooker') alongside a thoroughly modern treatment of the British Flora. It will be of altogether outstanding usefulness to botan- ists at all levels of study, not least to students in schools and universities, and to the many active amateur botanists of this country.

H. GODWIN

Advances in Genetics, vTol. IX. Edited by M. DEMEREC, published by Academic Press, Inc., New York, 1958. Pp. 294. Price $8.8o.

This number in the Advances in Genetics series is of particular interest to botanists, for of the six articles which it contains, three are concerned with fungi, one with dioecious flowering plants and one with interspecific hybrids in both flowering plants and animals. The sixth paper is by H. L. Carson on 'The population genetics of Drosophila robusta'. This species breeds on Ulmus americana and is thus confined to the deciduous forest of the eastern United States. Many different inversions of segments of the chromosomes occur in natural populations of the fly, and there are geographical and altitudinal clines both in external morphology and in the frequency of particular inversions.

In a review by H. P. Papazian entitled 'The genetics of Basidiomycetes' discussion is in fact limited to the Hymenomycetes and Gasteromycetes. Papazian is justifiably critical of some of the extravagant claims (for example, 'heterokaryotic mutagenesis') made by workers with these fungi, but he is perhaps not critical enough of some others. The genetic study of these fungi has as yet hardly begun and until a number of linked mutant genes are available in at least one species and until appropriate experiments have been performed using such genetic markers, it

This content downloaded from 62.122.73.17 on Thu, 12 Jun 2014 17:38:46 PMAll use subject to JSTOR Terms and Conditions

Reviews 407 is of little value to discuss such claims as the occurrence of somatic recombination between the nuclei of a dikaryon; the occurrence of a precise spatial distribution of the four spores on a basidium in relation to meiosis; the origin of new incompatibility alleles through crossing-over (unless supported by tetrad analysis, as in Papazian's own work); or inheritance through the nuclear sap!

By contrast, in 'Genetic analysis based on mitotic recombination' by G. Pontecorvo and E. Kifer, a sound experimental basis is shown to exist for the occurrence of two genetic pheno- mena of the greatest interest. These are mitotic crossing-over and mitotic haploidization, which have been shown to occur with low frequencies and apparently independently of each other in heterozygous diploid strains of Aspergillus nidulans and other filamentous fungi. In mitotic crossing-over, factors distal to the cross-over become homozygous while those between it and the centromere may remain heterozygous. Hence the sequence of genes on a chromosome and the position of the centromere can be mapped. In mitotic haploidization, whole chromosomes segregate and reassort, with the result that genes on the same chromosome show complete linkage. This enables the ready identification of the linkage group to which a mutant belongs. In 'An 8-chromosome map of Aspergillus nidulans', E. Kifer applies these methods, together with standard methods using meiosis, to map genes in A. nidulans. It is of interest that eight linkage groups were found, where only four had been anticipated from cytological studies. Comparison is made between mitotic and meiotic chromosome maps, and interesting differences are evident in the relative frequencies of occurrence of mitotic and meiotic crossing-over.

In an extensive review entitled 'The inviability, weakness and sterility of interspecific hybrids', G. L. Stebbins draws attention to important differences between plants and animals in the causes of hybrid inviability and sterility. In animals the most common cause of these conditions appears to be breakdown during differentiation of the diploid cells of the embryo and of the reproductive organs, respectively, while in plants these sources of hybrid inviability and sterility are comparatively rare. Stebbins attributes this difference to the higher degree of integration of parts in the animal, such that genic differences (between the parental species) affecting some primary growth process have manifold disturbing effects on development. The predominant source of hybrid inviability in Angiospermae is considered to be genic disharmony in the endo- sperm (with its unequal contributions from the two parents) or disharmonious interaction be- tween the embryo, the endosperm and the nucellus of the ovule, particularly (as D. H. Valentine has pointed out) between the latter two tissues. The chief source of hybrid sterility in plants appears to be structural differentiation of the chromosomes, such that the parental species differ by a number of inversions or interchanges of segments of chromosomes. In anirmals, structural changes seem to occur just as often, but (as M. J. D. White has pointed out) appear to play little part in causing hybrid sterility because the reproductive organs frequently break down before gamete-formation.

In a detailed and most interesting review of 'The mechanism of sex determination in dioecious flowering plants', M. Westergaard uses knowledge of biochemical genetics of micro-organisms as. a basis for a theory of how the sex-deciding genes act. He shows how all the observations are explicable within the normal framework of genetic systems. He emphasizes that nothing is therefore gained and much is lost by considering sexual differences to be in a distinct category from other individual differences, as has been advocated by M. Hartmann and by R. Goldschmidt. Westergaard is unable to accept H. J. Muller's argument that the rarity of polyploidy in animals compared with plants is because in dioecious organisms the progeny of tetraploids will predom- inantly be sterile intersexes. Perhaps the true explanation lies in Stebbins's idea that animals are in general more sensitive than plants to the disruptive effects on development of new combina- tions or proportions of genes.

H. L. K. WHITEHOUSE

Protoplasmatologia. Handbutch der Protoplasmaforschung (L. V. Heilbrunn and F. Weber, editors), vol. I, Z. Biocolloids and their Interactions. By H. L. Booij and H. G. BUNGENBERG DE JONG. IO x 7 in. Pp. I62 with I59 text-figures. Vienna: Springer- Verlag. i956. Price ?4 8s. 6d.

In an introductory book entitled Biocolloids and their Interactions the reader might expect to find a broad coverage of the field of colloids as applicable to biological systems, introduced possibly

This content downloaded from 62.122.73.17 on Thu, 12 Jun 2014 17:38:46 PMAll use subject to JSTOR Terms and Conditions