1915] 



ATKINSON PHYLOGENY IN THE ASCOMYCETES 349 



relation to the red algae. The analogy at least between the 

 trichogyne of the red algae and that of the Ascomycetes is 

 very striking. The evidence brought forward by Stahl (77) 

 and others of the relation of the trichogyne to the ascogo- 

 nium in the lichens, together with the fusion of spermatia to 

 the trichogyne, followed by the gradual and peculiar degenera- 

 tion of the latter and the subsequent development of the as- 

 cogenous threads, was generally accepted as proof of fertil- 

 ization in the ascogonium by a spermatium. Also the early 

 studies of Polystigma ruhrum (Fisch, '82; Frank, '83) and 

 Gnomonia erythrostoma (Frank, '86) in which similar struc- 

 tures and phenomena were observed at that time, were gen- 

 erally accepted as indicating a well developed condition of 

 sexuality. These studies gave a great impetus to the theory 

 suggested by Sachs ('96) that the Ascomycetes had their 

 origin from the red algae, or that the two groups had an- 

 cestors in common. This theory has taken very deep root 

 and probably is accepted by a majority of botanists even 

 at the present time, especially by those who are not special 

 students of the fungi. It should be stated also that a number 

 of our foremost students of the fungi, perhaps a majority of 

 them, are firm disciples of this theory. 



Recent investigation, however, including a cytological study 

 of several of the now classic types, including Collema (Bach- 

 mann. Miss F. M., '12, '13), Polystigma ruhrum (Blackman 

 and Welsford, '12; Nienburg, '14), Gnomonia erythrostoma 

 (Brooks, '10) have failed to furnish any evidence of a real 

 sexual function on the part of either the trichogyne or sper- 

 matia in any of the species of fungi possessing these two 

 structures. Pairing of nuclei in the oogonium, or the pairing 

 of these with nuclei from adjacent cells of the ascogonial 

 branch or archicarp, furnish the synkaria, or the synkaria are 

 organized at different stages in the development of the as- 

 cogenous hyphae (see Note iii). In some quarters these re- 

 sults have led to a loss of confidence in the sexual significance 

 of the trichogyne and spermatia of the Ascomycetes. Some 

 have therefore attributed to the trichogyne a physiological 

 significance of another kind, that of a respiratory organ for 



