418 ' BOTANICAL GAZETTE [December 



seen to occupy typical positions within it (fig. 34) . The endosperm 

 nucleus at the time of its formation by the fusion of its polar nuclei 

 and for some time thereafter contains two nucleoli. Later, how- 

 ever, but a single large nucleolus is visible (figs. 34, 35). 



Fertilization. — The writer has not investigated the details 

 of the germination of the pollen grain upon the stigma, nor of the 

 penetration of the pollen tube through the style into the ovarian 

 cavity. From what was observed, it appears that the pollen tube 

 enters the embryo sac in the usual way, displacing and disorganizing 

 the synergids (figs. 35, 37). 



The relative time of fusion of male nucleus with the egg was not 

 determined with certainty, but it probably remains for some time 

 in close proximity to the egg without fusion, during which time 

 the endosperm nucleus proceeds to divide actively. The first divi- 

 sion of the endosperm nucleus is followed immediately by the 

 formation of a cell wall (fig. 36). Hence it may be said that the 

 endosperm is "cellular from the outset of its development" (John- 

 son 9). The egg in Hedyosmum nutans, even when the endosperm 

 has reached the 4-celled stage, is still undivided and uninucleolate 

 (fig. 37). In Hedyosmum arbor escens the fertilized egg is still 

 undivided and binucleolate when the endosperm has reached the 

 10-12-celled stage (fig. 38). In the earliest stages of the 2-celled 

 embryo seen, the number of endosperm cells is approximately 100. 

 The endosperm continues to divide by longitudinal and transverse 

 walls and rapidly encroaches on the substance of the nucellus 

 (fig. 41). In the mature seed the endosperm has completely 

 crushed and absorbed all but one layer of the nucellar tissue, so 

 that the endosperm lies practically in contact with the inner 

 integument (fig. 43). The antipodals persist unchanged for 

 some time, but as the division of the endosperm continues they 

 begin to degenerate, and finally disappear altogether. The embryo 

 develops into a slightly elongated or oval mass of cells with a poorly 

 developed suspensor (fig. 43). 



The chief protection of the seed, except near the micropylar 

 end, where the inner integument is considerably thickened, is 

 afforded by the peculiar thick-walled, pitted cells of the carpel 





