TfiANSACTIONS OF SECTION K. 821 



the ingestion of solids -which it obtains by preying upon the bodies of plants and 

 other animals. The exigencies of its teeding have compelled the adoption by the 

 animal of the habit of locomotion, the development of an apparatus for the capture 

 of its prey, and of an alimentary canal for its introduction to the body, for its 

 digestion, and for the final ejection of the unused matter along with the waste 

 of the body. This has involved the concentration and the specialisation of the 

 individual. 



All this is, however, to you botanists but the commonplace of your laboratories 

 and lecture halls. But I have thought that it should be said, because this 

 fundamental difference of organisation between the two kingdoms is apt to bo 

 forgotten in discussions of problems of evolution, more particularly those of trans- 

 mission of characters and the effect of environment. This is es))ecially so when 

 they are approached from the zoological side. Were the point always recognised avu 

 should not have zoologists finding similarity between bud- variation in a tlowering 

 plant and the change in colour of the hair of a mammal. 



Of Origin and Dominance of the Angiospermous Type. 



It is now usually admitted that all plants, like all animals, have been derived 

 from aquatic ancestors, and that the trend of evolution has been in the direction 

 of the establishment of a vegetation adapted to a life on land. Of this evolution 

 the Angiosperms as we see them to-day are the highest expression. Can we say 

 anything about the origin of the angiospermous type ? As the problem presents 

 itself to me we can only mark time at present. 



From the geological record we obtain no help. The earliest traces of 

 Angiosperms in rocks of the middle jMesozoic period enable us to say little resrard- 

 ing them except that the fragments give evidence of an organisation as complete 

 as that possessed by the Angiosperms of the present day. The gap between the 

 angiospermous and other types of vegetation is a wide one, and no links are known. 

 Until further research provides specimens in a better state of preservation and 

 showing structure we can hope for little assistance from the geological record ; 

 and when we consider the circumstances in which the angiospermous plants as a 

 whole grow the prospect of such finds does not appear to be very bright. 



The appeal to ontogeny likewise gives us little information. Comparative 

 study does not establish connection with, only diflerentiates more and more, the 

 types of the Pteridophytes and Gymnosperms. The strong likeness of the 

 pro-embryo after the primary segmentation of many Angiosperms to the pro-embryo 

 of many Bryophytes has appeared a suihcient reason to some botanists for ascribing 

 a bryophytous parentage to the Angiosperms. Indeed it has been said that ' the 

 monocotylous embryo is the direct homologue of the sporogonium of the moss, the 

 cotyledon being homologous with tbe spore-producing portion of this out of which 

 it originated.' This anaphytic conception of the monocotylous embryo .*eems to 

 me to have as little real foundation as the hypothesis of its origin. The pro- 

 embryonic resemblance is interesting, but it may as well be homoplastic as 

 genetic. 



But if the information available to us does not permit of our building up a 

 pedigree for the Angiosperms, we are on surer ground when we endeavour to lix 

 upoii characters which have enabled the group to become established as the 

 dominant vegetation of our epoch. Before the era at which we have first know- 

 ledge of Angiosperms the earth's surface was, we know, clad with a dense vegeta- 

 tion composed of members of the various classes of Pteridophytes and Gymnosperms. 

 These appear to have existed in all the growth-forms which we know now amongst 

 the Angiosperms— Herb, Shrub, Tree, Liane. Yet they are now represented 

 amongst living plants by only a few remanent forms. Hordes of distinct forms and 

 whole classes have disappeared, giving place to plants of the angiospermous type. 

 There must then be some feature or features of advantage in this type over those 

 of the groups that previously occupied the ground, and through which it became 

 dominant. 



In considering this point we must bear in mind the well-known climatic 

 diferences— particularly in the distribution of •water— that distiuguisiieB our epoch 



1901. 3 H 



