NA TURE 



i8i 



THURSDAY, APRIL 14, 1910. 



THE CLAIMS OF LONG DESCENT. 



yfrdge iiber botanische Stammesgeschicte, ge- 

 alten an der Reichsuniversitdt zii Leiden. Ein 

 .chrbuch der Pflansensystematik. Zweiter Band, 



Jormophyta Zoidogamia. By Dr. J. P. Lotsy. Pp. 



<)02. (Jena : Gustav Fischer, 1909.) Price 24 marks. 



THE expectations aroused by the first volume of 

 this work, which dealt with the Thallophyta, will 

 not be disappointed by that now issued, in which are 

 included the liverworts, mosses, ferns and fern-allies, 

 and also the seed-producing plants that possess ciliated 

 male cells. In its wide compass are thus at the one 

 extreme types of a very low grade of complexity, while 

 at the otlier stands Ginkgo, long regarded as a true 

 conifer. The endeavour to trace the ancestn,- of the 

 tvpes in this range of forms raises many of the 

 most interesting and suggestive problems in 

 systematic botany, towards the answers to some of 

 which much progress has been made in recent years. 

 The contributions to their solution have been made 

 in a literature so scattered, and in so many languages, 

 that much of what has been published is difficult of 

 access, and is apt to remain unknown to students ; 

 hence the gain is great when it is collected, analysed, 

 and presented in clear and systematic form, especially 

 when accompanied, as it is here, with an excellent 

 bibliography and ample references to the original 

 sources of information. Such a work as this must 

 necessarily be ven.- largely a compilation if it gives 

 an adequate statement of the present state of know- 

 ledge and of the explanations put forward upon many 

 disputed questions; but the author has added to its 

 value by discussing these questions and stating the 

 reasons for and against the solutions advanced. 



While indication of relationships and of lines of 

 descent is, as the title of the. book implies, a promi- 

 nent feature throughout, its scope is much wider than 

 this, so that it is an admirable handbook to the study 

 of the structure and life-cycles of the groups discussed 

 in it. 



In a brief review it is not possible to note more than 

 a few of the many questions that arise in the con- 

 sideration of the plants included in this volume. These 

 plants agree in showing a cycle in which there is a 

 marked contrast between the gametophyte and the 

 ?porophyte, or the x- arjd the 2x-generations, as Dr. 

 -y prefers to express''them ; and they also have the 

 egonium recognisable, though obscured among 

 higher forms. The two great divisions of 

 ni.ploidales and Diploidales, characterised by the 

 dominance of the x- and the 2x-generations respec- 

 ''Y, express the recognition that recent discoveries 

 shown clearly the intimate relationships between 

 ferns and the seed-plants. .After discussing the 

 jtheses with regard to the origin of the Haploi- 

 5 and Diploidales, the author supports the view 

 ... .. they are derived by independent lines from Algae 

 of the group Isokonta. As to the origin of the anti- 

 '•"'ic generations in the cycle, he holds that the 

 > nee does not warrant a dogmatic conclusion; but 

 XO. 21 1 1, VOL. Ss] 



in discussing the homologies of leaf and stem in the 

 Diploidales he inclines to Potonie's hypothesis that both 

 represent specialised parts of a thallus, and may be 

 homologous with one another. Among the Haploidales 

 the evidence points more directly to the same con- 

 clusion. 



The structure and life-histories of a typical moss and 

 of a typical fern are set in contrast; and then follows 

 a similar account of a very simple (? primitive) tA'pe of 

 each, to ascertain in how far the supposed algal 

 ancestr\' can be traced. Then follows a survey of the 

 genera under each division, including every genus 

 that shows features of importance or interest, morpho- 

 logical or biological ; and not a few questions of 

 wider than mere systematic value are discussed 

 clearly and helpfully, as they arise in connection with 

 certain forms, e.g. under Hepaticae are discussed the 

 suggestion .that Anthoceros may represent a stage in 

 the development of the sporophyte in Diploidales, the 

 origin of the foliose habit, adaptations for economising 

 water in various types, the influence of light on dorsi- 

 ventral structure, &c. The wide range of structure and 

 of adaptability among Hepaticae is emphasised as in 

 marked contrast to the relative fixity of type among 

 the true mosses ; but among the latter many features 

 of biological import are duly noticed, such as the 

 methods of vegetative multiplication, and their rela- 

 tion in frequency to the greater or less difficulty in 

 securing the union of the male with the female cells. 

 The classification of the mosses into Acrocarpi and 

 Pleurocarpi is held to be too artificial, as is also the 

 importance attached to the rupture of the capsule in 

 the normal manner by a lid, those forms in which the 

 lid is not broken away being regarded as not forming 

 a related group, but rather as aberrant from various 

 families. Examples are quoted of very long-continued 

 vitality in the spores of certain mosses, up to fifty 

 years in a species of CEdipodium. The enlargement 

 and flattening of the apophysis in Splachnum, and the 

 growth of root-hairs from the seta in Eriopus, may 

 be regarded as efforts on the part of the sporophyte to 

 provide nourishment for itself; but they only em- 

 phasise the dependence of the sporophyte upon the 

 gametophyte among the mosses. 



In sharp contrast to them, in this respect, stand the 

 vascular plants or Diploidales, although for a brief 

 period, during early germination, the sporophyte fern 

 is as dependent on the gametophyte for nutrition as 

 is the moss-capsule. The dominance of the sporo- 

 phyte becomes always more evident as the adaptation 

 to life as land-plants becomes more complete, and as 

 the dependence on surface-water to allow of fertilisa- 

 tion of the ovum is done away with, until in the 

 Angiosperms it becomes difficult to trace the gameto- 

 phytes with certainty, and the sporophytes appear to 

 be themselves sexual, as was long the interpretation 

 of the structure of flowers. 



Dr. Lotsy gives a very helpful explanation of the 

 discoveries that in recent years have thrown so much 

 light on the affinities of the great divisions of the 

 Diploidales, and have broken down the distinction be- 

 tween Phanerogamia and Cr^-ptogamia, discoveries in 

 which the English-speaking races have taken so great 



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