l82 



NA TURE 



[April 14, 1910 



a part. It is now evident that the tendency to retain 

 the megaspore within the sporangium, and to continue 

 to nourish the gametophyte and also its offspring, the 

 sporophyte, through the sporangium until the young 

 sporophyte is provided with sufficient food in reserve 

 to enable it to begin life on its own account with a 

 fair prospect of success, resulting in the production of 

 the seed, has originated in widely different types, and 

 therefore on independent lines. Thus the true signi- 

 ficance of the seed, as an adaptation to secure the fuller 

 possession of the earth's surface, and to escape the 

 dangers of dependence on water for the fertilisation 

 of the egg-cell, has become realised. A new era in 

 botany opened with the recognition of the common 

 ancestry of ferns and cycads, based on similarities in 

 their structure, by the discovery that supposed ferns 

 of the Carboniferous strata produced true seeds re- 

 sembling those of cycads in important respects, and on 

 the not less startling discovery, which we owe to 

 Japan, of the ciliated male cells in the pollen of 

 Oinkgo and of the cycads. Of these and other great 

 advances in recent years, such as in the knowledge of 

 the Cycadeoidea, Dr. Lotsy gives a very clear account, 

 which should be most helpful to students. 



The vascular plants possessed of ciliated sperms, 

 the Zoidogamia, he divides into two great groups 

 •characterised by the sperm-cells, which possess two 

 'cilia in the Lycopodineae and their allies, and many 

 •cilia in the P"'ilicineae and seed-formers. He points out 

 that this agrees with the groups based by Lignier on 

 the structure of the leaves. Heterospory has been 

 ■attained independently in several lines of descent in 

 both these groups, and is thus no certain proof of 

 -close relationship among plants in which it occurs. 

 His arrangement is in several respects a good deal 

 different from that in use in English text-books, both 

 in the relations of the larger divisions and in such 

 minor details as breaking up Hydropterideae and 

 placing Marsiliacege beside Schizaeaceae, and Sal- 

 viniaceae beside HymenophyllaceEe, among the lepto- 

 sporangiate filices. 



On similar grounds Selaginella is brought back to 

 Lycopodiaceae, while Isoetes is placed between the 

 Equisetaceae and Filices, because of its polyciliate male 

 cells and of the development of its spores and embryo. 

 The present state of knowledge with regard to the 

 ■structure and life-histories of the Lycopodiaceae and 

 their allies is in striking contrast to that of not many 

 years back ; and of this advance the author gives a 

 ^ood account. The relations of the alliance to other 

 groups can now be estimated in a truer light than 

 was formerly possible. Though certain types within 

 it had advanced far on the way to the formation of 

 seeds, there is no clear evidence pointing to the de- 

 scent from them of any existing seed-plants. 



The lectures treating of the ferns and their allies are 

 of very special interest, in view of the ever-increasing 

 evidence connecting them with the descent of the 

 seed-plants. While the progress during the past 

 decade has been very great, and has revolutionised 

 former beliefs, it has shown also that the production 

 of seeds had already been attained at a period so far 

 back in geological historj^ as to make it very im- 

 probable that direct proof of the lines of evolution will 

 NO. 21 1 1, VOL. 83] 



be obtained. But while great problems will probably 

 remain unsolved in detail, the general trend of pro- 

 gress has become evident, and there is reason to anli- 

 cipate that the rate of advance will not slacken ; 

 though it seems scarcely likely that there can be many 

 future discoveries so startling as those already 

 alluded to. 



The grouping of the leptosporangiate ferns takes 

 full account of Prof. Bower's researches on the spor- 

 angia. The eu-sporangiate types, like the leptosporan- 

 giate, are derived from the Primo-filices, by separate 

 lines of descent. The Pteridospermeae are probably 

 more nearly related to Marattiaceae than to any other 

 existing ferns, but over a very wide gap. The con- 

 cluding lectures of this volume treat of the Cordaitales, 

 Bennettitales, Cycadales living and extinct, and 

 Ginkgoaceae. They present subjects of extr-eme in- 

 terest, and of the utmost importance in tracing the 

 development of the higher planis. 



Those who read this volume will feel that while it 

 demands close attention, and while some of the lec- 

 tures are of value for reference on subordinate groups 

 rather than for questions of wider interest, the work 

 well repays the attention necessary, and that the aim, 

 kept steadily in view, has been successfully attained, 

 to supply an unbiassed and worthy representation of 

 what is at present known with regard to the groups 

 of plants discussed. The information brought to- 

 gether within its compass has been gathered from a 

 vast field ; and the sources from which it has been 

 taken are scrupulously indicated, as regards both text 

 and the excellent and copious illustrations, which do 

 much to aid the exposition, clear though that is. We 

 cannot but feel that it is more useful in its present 

 form, available to be read and re-read, than it could 

 be as a course of lectures. It must prove a great boon 

 to students desirous to obtain an adequate guide to the 

 researches of recent years, in a form that can permit 

 of use as a work of constant reference, from which 

 they may gain wider views of the science of botany. 



The third volume, on siphonogamous seed-plants, 

 will be most welcome, though it can scarcely deal 

 with subjects of such interest, or so full of the charm 

 of advancing knowledge. The standard of the two 

 volumes already published is a guarantee for the ex- 

 pectation that it will be a most valuable addition to 

 every botanical library. 



UTILISATION OF PEAT. 

 Commercial Peat : its Uses and Possibilities. By 

 F. T. Gissing. Pp. x+191. (London: Charles 

 Griffin and Co., Ltd., 1909.) Price 6s. net. 



IN this volume on peat, which is a companion one 

 to that published in 1907 by Messrs. Bjorling and 

 Gissing, the author's aim is the description, from a 

 commercial point of view, of the various processes pro- 

 posed for the utilisation of peat. 



In pursuance of this object Mr. Gissing describes 

 fully the preparation from peat of alcohol, moss litter, 

 and paper, the cutting and drying of peat, and the 

 manufacture of press turf and of machine turf, but 

 the greater part of the book deals with the products 

 got by the destructive distillation of peat. 



