1915] 



ATKINSON PHYLOGENY IN THE ASCOMYCETES 



355 



highly specialized ones as Sachs (74, '96), de Bary ('81, 

 '84), and many other students have advocated, the female 

 organ or archicarp first appeared as a " unicellular ' ' or con- 

 tinuous organ, not differentiated into an oogonium or fertile 

 portion, and a trichogyne. The presence of a " 



1 ' procarp, ' ' 



whether consisting of one or several cells, which ultimately 

 gave rise to the asci or ascogenous threads was the predomi- 

 nant character which led Sachs in 1896 to believe in the phy- 

 letic relation of the sac fungi and red algae, although earlier 

 he had regarded the morphology of the ascocarp and cysto- 

 carp of greater importance in showing relationship. No 

 known red alga possesses a procarp simple enough to repre- 

 sent the prototype of the two groups. Gymnoascus was se- 

 lected by Sachs as representing the simplest Ascomycetes. 

 The archicarp of Gymnoascus is a continuous structure more 

 or less coiled around the antheridium from which it copulates 

 directly without the intervention of a trichogyne. 



After copulation the ascogonium divides into several cells 

 which give rise to the ascogenous hyphae. In some forms the 

 splitting up of the ascogonium by transverse division occurs 

 at an earlier period, before copulation. There is some evi- 

 dence which indicates that the ' * trichogyne ' | in the Ascomy- 

 cetes primarily was a prolongation of the " unicellular ' ' 

 oogone (or carpogone), and that when it was first separated 

 as a distinct cell it was still a fertile part of the archicarp. In 

 Aspergillus repens the terminal cell, or "trichogyne," some- 

 times gives rise to ascogenous hyphae (Fraser, '08). 



The terminal cell became merely a trichogyne when it ceased 

 to give rise to ascogenous hyphae, and acted as a transport 

 tube for the sperm nuclei from the antheridium to the as- 

 cogonium, as in Pyronema and Monascus. The septum be- 

 tween the terminal cell and the functional ascogonium was 

 an impediment to the passage of the sperm nuclei, as well as 

 the fact that when they entered the terminal cell of the archi- 

 carp they did not meet with functional egg nuclei. This situa- 

 tion very likely favored the assumption of sperm and egg 

 functions by the nuclei of the functional ascogonial cell. The 

 variations in Pyronema where the antheridium may or may 



