APOGAMY, APOSPORY, AND PARTHENOGENESIS 



313 



(d) There is no female organ: fusion takes place between two adjacent 

 tissue-cells of the gametophyte ; the sporophyte is developed from 

 diploid cells [''grafted tissue"] thus produced, but there is no 

 proper zygote as there is in a, b, and c: observed (Farmer [and 

 Digby] 1907) in the prothallium of certain ferns (Lastrcea pseudo- 

 mas, var. polydactyla} [Fig. 124, A] : male organs (and sometimes 

 female) present but functionless. Another such case is that 

 of Humaria rutilans (ascomycete), in which nuclear fusion 



v--*v*x / w i. & * " 



' 



i >Mm** Jf- 



FIG. 125. 



A, cell fusion in the sporangium of Aspidium falcatum. X 1950. (After R. F.Allen 

 1911.) B, incomplete nuclear division in sporangium of Nephrodium hirtipes. X 1250. 

 (After Steil, 1919.) C, apogamy and sporophytic budding in the embryo sac of Alchemilla 

 pastoralis: egg developing apogamously below; cell of nucellus forming an embryo above; 

 two polar nuclei and one synergid nucleus at center. (After Murbeck, 1902.) 



has been observed (Fraser 1908) in hyphse of the hypothecium : 

 the asci are developed from these hyphae, and in them meiosis 

 takes place; there are no sexual organs. [A similar condition 

 has been reported in Helvella crispa (Carruthers 1911) and 

 Polystigma rubrum (Blackman and Welsford 1912). It has 

 already been pointed out (p. 291) that many students of the 

 ascomycetes deny the existence of a nuclear fusion in the 

 archicarp or vegetative cells, holding rather that the only 



