230 THE SCOTTISH BOTANICAL REVIEW 



As to their taxonomy, he writes : — 



" The Angiosperms are separable into two diverging subclasses — 

 the monocotyledons (Monocotyledoneae), and the dicotyledons 

 (Dicotyledonese), the first ranking structurally lower than the second. 

 The monocotyledons are well divided by Bentham and Hooker into 

 seven series, and these we may accept unchanged, with the single 

 exception that the water-worts (Hydrocharitaccce) should probably 

 be removed from the Microspermse to constitute an additional 

 co-ordinate group. These eight groups, which appear to be 

 deserving of no more than ordinal rank, should then be arranged 

 so as to have the following sequence, namely, Apocarpse, Coronarieae, 

 Nudifloras, Calycin^e, Glumacese, Hydrales, Epigynse, Microspermse. 

 Here it must be understood that the Nudiflorse, Calycin^e, and 

 Glumacese are separate orders radiating from the present order 

 CoronarieEe, and that the Hydrales constitute a diverging order 

 from the base of the Epigynae." 



Some researches made by Professor H. H .W. Pearson ^ in regard 

 to Welwitschia are of interest in this connection. In studying the 

 endosperm he found all the cells are multinucleate. Later, each 

 cell possesses only one nucleus by fusion of nuclei in young cells. 

 The original nucleus by division has become a thousand. The 

 embryo-sac elongates, and there is a redistribution of nuclei. Two 

 poles are formed : one at the micropylar, the other at the opposite 

 end. In the former the nuclei are not crowded, in the latter they 

 are. Then a division into compartments or segmentation takes 

 place, with 2 to 6 nuclei at the micropylar end, 1 2 or more elsewhere. 

 When there are more than 6 nuclei they are divided up into cells 

 with single nuclei ; but those at the micropylar end are not so 

 affected, as each wall grows up into the prothallial tube. The 

 nuclei and cytoplasm pass into this, and the nuclei become 

 functional gametes. This unusual characteristic has led Professor 

 Pearson to regard the endosperm -as representing a new stage, which 

 he calls the trophophyte, which serves to mark its intercalation into 

 the life-history — a terminology now familiar to us from Professor 

 Bower's theory of the antithetic generation or intercalation of the 

 sporophyte into the life-history of the moss plant. This trophophyte 

 is neither the sporophyte nor gametophyte, but is regarded as 

 phylogenetically related to the endosperm of Angiosperms by a 

 series of reductions and specialised stages. The fact that in Angio- 

 sperms a similar procedure takes place is corroborative of this view. 

 In a more recent paper - Professor Pearson finds that the ovule in 

 Welwitschia is cauline, and it is considered that the female cone 

 and male flower are derived by reduction and specialisation from an 

 amphisporangiate strobilus of a type similar to Bennettites. After 

 division 1024 nuclei are contained in the embryo-sac, and it is 

 repeatedly divided. The endosperm of the primitive Angiosperm 



^ "Rep. Brit. Assoc. Dublin," 1908. 



"^ " Further observations on Welwitschia,'''' " Proc. Royal See," Nov. 1908. 



