• 52 SUMMARY OF CURRENT RESEARCHES RELATING TO 



numerous sporophytes. These sporophytes arc noteworthy in that they 

 are the product of the union of two diploidic elements. They are io 

 fad tetraploidic plants. The aumber of chromosomes in the nuclei of 

 the archesporial tissue is four times that of the sexif erous phase in the 

 Qonnal plant. And in the resulting spores this number is reduced 

 to 'In. Further, by regeneration the tetraploid capsules yield a proto- 

 iiema which produces weak flowering shoots, hitherto incapable of 

 fertilization, so far as experimentation has gone. Thus there is an 

 essential difference between dioicous and monoicous mosses. The 

 diploidic races obtained from the former have abnormal flowers, which 

 are bisexual but sterile, and can only be reproduced vegetatively. On 

 the other hand, the diploidic races obtained from monoicous mosses 

 have normal sexuality and can be reproduced by sporogenesis. The 

 reproduction of aposporic forms is of great interest to systematic 

 bryologists. For if, as the result of wounds, such forms are frequent in 

 nature, it may become possible to explain the polygamy found in some 

 species of Bryum, and sterility in some dioicous species. The diploidic 

 state reveals itself in a notable increase in the size of the cells, the 

 nuclei, and the reproductive organs. 



Spermatogenesis in certain Hepaticae.* — W. L. Woodburn gives 

 the results of his investigations of spermatogenesis in certain hepatics. 

 He finds no evidence of the occurrence of centrosomes in the spermo- 

 genous tissue of Porella and Asterella, or of Marchantia and Fegatella. 

 In his preparations he could find nothing such as Van Hook observed 

 in the dividing vegetative cells of Marchantia, Mottier in Dktyota, 

 Farmer in the germinating spores of Fegatella and Pellia, and Farmer 

 and Reeves in Pellia. Further, there is no evidence that the centro- 

 some persists in the resulting sperm-cell. The occurrence of such a 

 body sometimes at the pole of the spindle does not necessarily imply 

 more than a probable concentration of cytoplasmic or kinoplasmic 

 materials. The development of the blepharoplast in all these plants 

 proceeds from a dense granular mass of cytoplasm located in the most 

 distant angle of the sperm-cell. The blepharoplast becomes a cord, 

 growing in close contact with the plasma membrane and entirely past 

 the nucleus. The latter then draws out along the posterior portion of 

 the blepharoplast and may extend beyond it, while from near the 

 forward and slightly enlarged end two cilia develop. Ikeno's " cyto- 

 plasmatischer Fortsatz" is probably merely a part of the blepharoplast. 

 No body corresponding in size and appearance to the " Nebenkorper " 

 of Ikeno was found. Whereas some authors regard the mature sperm 

 as representing three metamorphosed elements of the cell (nucleus, 

 cytoplasm, and blepharoplast or centrosome), the author prefers to hold 

 the view that the blepharoplast in Porella, Marchantia, and Fegatella, 

 where no centrosome exists, arises de novo in the cell in which it is to 

 function as the cilia-bearer. This is in keeping with the views of 

 Escoyer and Mottier. The mature sperm represents in its head the 

 nucleus, in its blepharoplast and cilia the specialized parts of the 

 cytoplasm, the remainder of the latter being found in the cytoplasmic 

 vesicle. 



* Ann. of Bot., xxv. (1911) pp. 299-313 (1 pi.). 



