No. 464.] STUDIES ON PLANT CELL. VII. 565 



embryos when the conditions permitted of fertilization. We 

 shall refer to some general considerations of Lang in our sum- 

 mary and conclusions on apogamy. 



The spermatophytes present some exceedingly interesting 

 examples of apogamous developments of embryos from nuclei 

 within the embryo-sac other than the egg, as from antipodals 

 (Allium odorwn, Tretjakow, '95 ; Hegelmaier, '97) or synergids 

 (AlcJiemilla sericata, Murbeck, : 02) or nuclei in the endosperm 

 (Belanophora, Treub, '98 ; Lotsy, '99) but in these cases the 

 sporophyte number of chromosomes is apparently present 

 through a suppression of the reduction phenomenon of sporo- 

 genesis in the development of the embryo-sac. 



We will now consider two studies which describe nuclear 

 fusions preliminary to the appearance of apogamy (Blackman, 

 :O4a; Farmer, Moore, and Digby, :O3). 



Blackman's (: O4a) observations on Phragmidium have cleared 

 up to a great degree our understanding of the life history of the 

 Uredinales. The chains of secidiospores have been found to 

 arise serially from "fertile cells" which form a group at the 

 spot where an aecidium is to be developed. Each fertile cell 

 has above it a sterile cell which, however, breaks down. The 

 sterile and the " fertile cell " together may represent a female 

 sexual organ, the sterile cell perhaps standing for the remains of 

 a receptive structure similar to a trichogyne. The spermogonium 

 consists of a large mass of antheridial filaments that abjoint 

 sperms which are no longer functional. It is of course uncer- 

 tain whether the " fertile cells " are morphologically the original 

 female gametes since they may readily be other cells drawn into 

 the process of apogamy. The " fertile cell " is stimulated to 

 activity by the entrance of a second nucleus either from an 

 adjacent hypha or from the cell below. The second nucleus 

 does not fuse with the original nucleus in the "fertile cell " but 

 the two come to lie close together as a paired or conjugate 

 nucleus. The two nuclei of the pair divide simultaneously 

 (conjugate mitosis) throughout a long series of nuclear divi- 

 sions, beginning with the formation of aecidiospores and through 

 the vegetative history which follows up to the production of the 

 teleutospores where the members of the last pairs unite to form 



