HIGHER FUNGI 1 23 



following fecundation in SphcBrotheca, Pyronema and Collcma, and in 

 such red algae as Batr actios permum, Nemalion and Dudresnaya. A 

 sketch of the process will not be amiss. The antheridia and oogonia 

 arise in Pyronema from the apical cells of thick hyphal branches, 

 which arise vertically from the substratum. These organs stand side 

 by side. Soon a trichogyne is formed on the oogonium, as a papillar 

 outgrowth, and subsequently it is cut off from the oogonium proper by 

 a transverse wall. The antheridium and oogonium are multinucleate 

 from the start and a broad stalk cell is cut off from the base of the 

 oogonium. The tip of the trichogyne curves over to meet the tips of 

 the antheridium, and the wall between them is dissolved enough to 

 form a pore by which the cytoplasm of one organ becomes continuous 

 with the cytoplasm of the trichogyne in which the nuclei have already 

 disintegrated. The antheridial nuclei migrate into the trichogyne, and 

 while this is happening the nuclei of the oogonium move to the center, 

 where they become collected into a dense, hollow sphere. Now the 

 basal wall of the trichogyne breaks down and the antheridial nuclei 

 pass into the oogonium and become mingled with those of the egg cell. 

 The antheridia and carpogonial nuclei now become paired without 

 fusing. Out of the oogonium grow ascogenous hyphae and the paired 

 nuclei pass into them. The young ascus develops from a penultimate 

 cell of a bent ascogenous hypha with two nuclei which fuse, after the 

 ascus has been formed and this fusion represents a sexual process. The 

 end cell of the ascogenous hypha and the stalk cell are uninucleate, 

 and these two cells may fuse to form a binucleate cell out of which a 

 penultimate cell may arise. This single nucleus of the ascus then 

 divides to form the series of eight ascospores usually found in the ascus. 

 The synapsis stage of this single nucleus is immediately followed by a 

 reduction division. 



Claussen^ has found that the formation of the ascus is not as simple 

 a process, as described by Harper, and he has added materially to our 

 knowledge by his reinvestigation of Pyronema confluens (Figs. 38, 39 

 and 40). He finds that the conjugate nuclei do not fuse in the asco- 

 gonium (carpogonium), nor in the ascogenous hyphae, nor in the pen- 

 ultimate cell, nor when the tip cell of the ascogenous hook fuses with 

 the stalk cell to form a binucleate cell. He finds that the penultimate 



1 Claussen, p.: Zur Entwickelungsgeschichte der Ascomyceten, Pyronema con- 

 fluens. Zeitscrift fiir Botanik, 4, Jahrgang, Heft: 1-64 with 6 plates. 



