No. 526] SEXUAL REPRODUCTION IN ANGIOSPERMS 61 7 



sary, both from the standpoint of phylogeny and from 

 that of the individual, or individuals concerned. Careful 

 investigations of recent years upon the cells of certain 

 lower plants seem to justify the opinion that the more 

 original or primary protoplasm is to he conceived as be- 

 ing entirely without organized nuclei, possessing uni- 

 formly in all parts its formative and nutritive functions. 

 Then there gradually came about, phylogenetically speak- 

 ing, a separation of the constructive, nutritive— and may 

 we also say— directive functions in this substratum, those 

 parts of the plasm having formative activities being the 

 first differentiated bearers of hereditary characteristics. 

 These particles or granules may have remained for a long 

 time distributed in the general plasmic mass, just a- we 

 find in certain existing Cyanophycese ami bacteria 

 "chromatin bodies" distributed throughout the cell 

 rather than collected in a typical nucleus. The next 

 step in the evolution of more differentiated protoplasm 

 occurred when the formative parts, be they known as 

 chromatin bodies, or what not, became separated from 

 the surrounding plasm by a membrane, or. in other words, 

 the creation of nucleus as distinct from cytoplasm. In 



believe that among the lower plants the nucleus is as 

 highly differentiated as among seed plants, consequently 

 a larger number of functions must have been performed 

 by the various hereditary units, and a much simpler 

 method of nuclear division demanded. This view seems 

 well borne out by the simpler method of nuclear division 

 in certain lower plants and in cells of higher plants, 

 which have taken on a purely vegetative role, and which 

 divide by the direct method or fragmentation. As soon, 

 however, as differentiation in the hereditary units in- 

 creased, a much greater complexity in the mechanism 

 of division followed, a conclusion to which the mitotic 

 phenomena in higher plants stand as incontestible testi- 

 mony. On the other hand, we do not mean to imply 

 that' progressive differentiation was confined to the 

 nucleus alone, for the cytoplasm of higher plants reveals 



