114 



DISCOMYCETES 



[CH. 



pairs (fig. "JO a), giving rise to the larger. Sometimes in connection with 

 this process a nucleus migrates through the wall from one cell to another 

 (fig. 70 b), as in prothallia of ferns. Thus in H. rutilans, where the sexual 

 organs are completely lacking, normal fertilization is replaced by the union 

 of vegetative nuclei in pairs. 



Fig. 70. Humaria rutilans (Fr.) Sacc. ; u,. fusion in a vegetative hypha ; b. migration 

 of nucleus from one vegetative cell to another; both x iioo. 



The cells which contain fusion nuclei now give rise to ascogenous 

 hyphae, while, from the rest, the paraphyses and cells of the outer sheath 

 arise. 



The asci are very large, and their nuclei particularly clear. The number 

 of chromosomes in the nuclei of the ascogenous hyphae, and in the first 

 and second divisions in the ascus and in the prophase of the third is sixteen 

 (figs. 71, 72). In the third telophase eight have been recorded by Maire and 

 by Eraser (fig. 73), and sixteen by Guilliermond (fig. 74). 







l;r,.-. 



Fig. 71. Humaria rutilans (Fr.) Sacc; a. asco- 

 genous hypha showing sixteen chromosomes in 

 each nucleus, x 1950; b. fusion nucleus of ascus 

 passing out of synapsis, x 1300; c. fusion nucleus 

 of ascus showing sixteen gemini, x 1950. 



