1915] 



ATKINSON PHYLOGENY IN THE ASCOMYCETES 365 



exactly as male gamete of Zygorhynchus is formed, except the 

 latter is multinucleate. By disappearance of the separating 

 wall, ascus is formed of the two gametes. 



Endomyces series, then, derived from Dipodascus-YikQ an- 

 cestors, with Endomyces Magnusii the lowest and most gen- 

 eralized. 



Developmental tendencies from here in four, five, or six 

 different directions : 



1. Eremascus, both gamogenic branches uninucleate, ascus more 

 definite and specialized in shape. Loss of conidial formation. 

 Endomyces fibuliger indicates step toward Eremascus (E. fer- 

 tilis) in small size of gametes. 



2. Endomyces diverging into the two series, one chiefly with sprout 

 conidia, the other chiefly with oidia; the latter preserves the E. 

 Magnusii character, the former takes on sprout conidia in addi- 

 tion to oidia (E. fibuliger and E. capsularis form both oidia and 

 sprout conidia) ; oidia formation the more primitive and gener- 

 alized condition in Ascomycetes. 



3. Saccharomycetes. Still more specialized and reduced than in 

 Endomyces fibuliger and in this same line. Schizosaccharomyces 

 may have come from same line with dropping of sprout conidia, 

 or may be descended from form near Endomyces Magnusii. 



4. Exoascaceae. From Endomyces-like ancestors. Nuclear phe- 

 nomena not well known. Diploid young ascus may have arisen 

 in connection with cell wall formation, two nuclei being retained 

 in ascogone instead of one as in E. Magnusii, where all but one 

 are excluded at time of wall formation, i. e., ascus fundament 

 may have retained the polyenergid character of the most primi- 

 tive forms like E. Magnusii. Tendency to form hymenia may 

 be controlled by host since asci in all, except Taphrina laurencia, 

 come to surface to mature. 



5. Ascocorticium, saprophytic on wood where food is not so rich, 

 tendency to drop conidial formation (?), association of asci in 

 hymenium, highest development of the Endomyces series, or of 

 the Protoascomycetes. Series is terminated early, tendency in 

 Endomyces line to specialization of zygote into one ascus with 

 reduced number of spores, and line soon terminated. 



6. Ascoidea, Protomyces, Taphridium, etc., probably represent 

 forms derived by reduction and loss of distinct sexual organs but 

 preserving primitive feature of many divisions of nucleus in the 

 generalized ascus. 



II. EuASCOMYCETEs. Lowcst forms with generalized archi- 

 carp. Similar to Monascus, Gymnoascus, etc. 



