624 



NATURE 



[February 12, 1920 



THE ORIGIN OF PLANT LIFE ON LAND. 



Thalassiophyta and the Suhaerial Transmigration. 

 By A. H. Church. (Botanical Memoirs, No. 3.) 

 Pp- 95- (London : Oxford University Press, 

 igig.) Price 35. 6d. net. 



MR. CHURCH has produced a very serious 

 contribution to the discussion of the 

 sources of plant life on land. No one interested in 

 this question can neglect his work. The statement 

 is attributed to Weismann that the birthplace 

 of all animal and plant life lies in the 

 sea. Mr. Church circumscribes that thesis in 

 his opening words, "The beginnings of botany 

 are in the sea "; and his essay has as its object 

 to demonstrate that the land flora originated, as 

 the primal land-surfaces rose gradually above the 

 ocean, from a marine flora already fixed upon its 

 shores. He designates as " Thalassiophyta " the 

 whole of the salt-water vegetation, and as " Xero- 

 phyta " the whole of the land flora. The former 

 he divides again into Plankton and Benthos, point- 

 ing out that Plankton responds to the single factor 

 of water, Benthos to the two factors of water and 

 substratum, while Xerophyton responds to the 

 three factors of water, substratum, and air. His 

 main thesis is that the last was derived from the 

 higher types of Benthos. " Processes of conduc- 

 tion and absorption involving roots and tracljeides 

 are initiated, and such departures superimposed on 

 a seaweed soma." "The tetraspores of the sea 

 become ' homosporous,' air-dried, and wind- 

 borne " (p. 44). 



Thus the evolution of a land flora was a phase 

 of transition in situ rather than involving a preli- 

 minary landward migration, via fresh water. The 

 successful transmigrant alga? of the first land 

 migration combined the best and highest factors 

 of marine equipment, as illustrated in many sur- 

 viving groups. At the outset Mr. Church sepa- 

 rates the problem of this migration from the origin 

 of a cytological cycle, maintaining that the latter 

 was already established before the migration took 

 place. For these conclusions argument is pro- 

 duced rather than fact ; indeed, there appears to 

 be no new body of fact in the whole memoir. The 

 author remarks incidentally that homoplasy and 

 convergence have been much neglected. We 

 agree; but may not they explain much of what he 

 interprets as evidence of a direct migration? 



Two serious omissions appear in the memoir. 

 There is no reference to the important discoveries 

 of T-ower Devonian fossils in the Rhynie Chert, 

 though the description of Rhynia was published 

 early in 1917. Kidston and Lang give positive 

 fact as to the structure of one of the earliest known 

 land-plants ; and secure fact is worth a vast 

 NO. 2624, VOL. 104] 



amount of surmise and argument. Nor does Mr. 

 Church refer to the question of transference of the 

 tetrad-division in the course of descent to a fresh 

 position in the life-cycle, though Svedelius had 

 raised that question in 1916, and adduced facts 

 very pertinent to it. Such facts, and the argu- 

 ments that may be based upon them, might, if 

 they had been taken into account, have materially 

 affected Mr. Church's statements. 



Notwithstanding such omissions, the memoir is 

 a real contribution to morphological thought. It 

 may be that Mr. Church has over-accentuated the 

 directness of the origin of land-plants from marine 

 forms, fkit he has carefully protected himself by 

 saying that "no Phasophycean or Floridean 

 passed on to higher autotrophic land-flora " (p. 42). 

 The cautious philosopher, while sympathising with 

 Mr. Church's general thesis, would probably 

 prefer to give greater elasticity to it, seeing in the 

 modern marine flora suggestions upon which to 

 base hypotheses rather than those blunt state- 

 ments of conclusion which find their place in Mr. 

 Church's pages. However that may be, the effect 

 of "Thalassiophyta" will be to direct attention, 

 which was already swinging that way, more defi- 

 nitely towards marine rather than to fresh-water 

 alga;, as a probable source of land vegetation. 

 Though some of Mr. Church's conclusions mav 

 not find wide acceptance, the memoir is the most 

 thoughtful contribution to the question in recent 

 years, and it is full of originality and of interest- 

 ing though bluff criticisms. F. O. B. 



NORMAL AND MORBID PSYCHOLOGY. 

 Mind and its Disorders: A Text-book for Students 

 and Praciitioners of Medicine. By Dr. W. H. B. 

 Stoddart. Third edition. (Lewis's Practical 

 Series.) I*p. xx + 580. (London: H. K. Lewis 

 and Co., Ltd., 1919.) Price iSi'. net. 



ARI'^XILW of the new edition of this well- 

 known text-book is justified by extensive 

 modifications corresponding to the author's con 

 version to the doctrines of Freud. The volume 

 contains in 572 pages an account of normal and 

 morbid psychology — including the tracing of all 

 mental processes in psychological terms to their 

 original elements and their correlation with their 

 neural equivalents — of the clinical forms of all the 

 neuroses and psychoses and their investigation 

 and treatment, of the diseases to which the insane 

 are specially liable, and of the legal relations of 

 insanity. 



Most modern problems in all these subjects are 

 touched upon, and the book provides the sort of 

 knowledge required by the student and general 

 practitioner and a starting point from which the 



