154 HISTORY OF BOTANY 



is remembered, together with the fact that in the discovery 

 of Sporogonites by Halle the early existence of moss-like 

 plants is now established." After referring to work by 

 Kidston and Lang at present in progress, Bower con- 

 cludes : " The new facts have put theoretical morphology 

 again into the melting-pot, and there is every reason to 

 expect that it will emerge strengthened and refined. " 



(3) The labours of Hofmeister had done much to 

 demonstrate the continuity between the Pteridophyta 

 and the Phanerogams. The first group to be linked up 

 with the Pteridophyta was the Gymnospermae, and the 

 general tendency, at least from 1890 onwards, was to 

 connect this group more closely with the Vascular Crypto- 

 gams than with the Angiosperms. Thus in 1891 Belajeff 

 showed that the Gymnosperm pollen grain gave rise to 

 something that could be homologised with the antheridium 

 formed in the microspore of Selaginella, and this homology 

 was greatly strengthened by the discovery of motile 

 sperms in Ginkgo by Hirase in 1895, in Cycas by Ikeno 

 in 1896, and in Zamia by Webber in 1897. 



While the stamen and pollen-sacs of the Cycadaceae 

 could be readily correlated with the microsporophylla 

 and microsporangia of the Pteridophyta, there was 

 nothing among living members of that group that appeared 

 comparable to the ovule and its embryo-sac. Coulter and 

 Chamberlain in their work on the Morphology of Gymno- 

 sperms, first published in 1910, suggest that " the oldest 

 ovule had a single integument entirely free from the 

 nucellus ; in testa-formation this integument differenti- 

 ated into three layers, the outer fleshy, the stony, and 

 the inner fleshy ; the ovule was supplied with two sets 

 of vascular strands, the outer traversing the peripheral 

 region of the nucellus ; and the beaked tip of the nucellus 

 broke down more or less completely within the firm and 

 resistant epidermis to form a pollen chamber." I must 

 return to this subject presently in discussing the inter- 

 pretation of the parts of the flower. 



