150 HISTORY OF BOTANY 



producing generation of Bryophyta this removal from 

 external influences and exposure to the maternal influence 

 of the sexual generation last practically throughout the 

 development of the sporogonium. In the Pteridophyta 

 the asexual generation ultimately becomes free from the 

 prothallus. In all cases however the development is 

 initiated and has advanced to the establishment of the 

 various organs of the sporophyte under the maternal 

 influence. We are justified in assuming from some 

 particular cases which have been studied that each stage 

 in the ontogeny is determined by the preceding stage. 

 If, therefore, as in the Pteridophyta, the first steps of 

 development have taken place under the influence of the 

 prothallus, the influence of the preformed parts of the 

 young sporophyte may be legitimately assumed to 

 exercise a ' formative induction ' on the further course 

 of its development." 



Lang's statement of his theory aroused an important 

 discussion at a special meeting of the Linnean Society 

 in February 1909, which was taken part in by supporters 

 of both the homologous and antithetic hypotheses, but 

 the views expressed, as also the critical paper published 

 some time afterwards by V. H. Blackman, I must leave 

 you to read for yourselves. Farmer, one of the botanists 

 present at the Linnean discussion, while admitting the 

 importance of Lang's work, denied that " any insight 

 was afforded thereby into the causes which, in the first 

 instance, were responsible for the cyclical alternation, 

 or that the rival claims of the homologous and antithetic 

 theories were capable of being decided on such lines." 



Bower's present position may be best understood 

 from the following sentences extracted from his recently 

 published book, Botany of the Living Plant: "The 

 origin of the sporophyte in the Archegoniatae is quite 

 problematical, since no certain ancestry is known for 

 them. It has been suggested, on the one hand, that the 

 dependence of the sporophyte upon the gametophyte 



