1915] 



ATKINSON PHYLOGENY IN THE ASCOMYCETES 



367 



represent reduced forms derived on the one hand from the Pha- 

 cidiales and perhaps on the other from the Sphaeriales and pos- 

 sibly some from the Perisporiales. The formation of the char- 

 acteristic shield has rendered superfluous the perithecial wall as 

 a protective structure. The genus Diplocarpon, the structure 

 and development of which was investigated by one of my former 

 students (see Wolf, '12), I believe is an excellent illustration of 

 a form on the way (by reduction of the perithecial wall in con- 

 junction with the formation of the shield) from the Phacidiales 

 to the condition presented by many members of the Micro- 

 thyriales. 



The above provisionally suggested relationships may be 

 represented by the following five or six series, or lines of 

 development, with the accompanying diagram (fig. 10) : 



1. Apocarp line from Dipodasc us-like forms and by reduction. 



2. Plectocarp line from Dipodascus-like forms, perhaps similar to 



Monascus. 



3. Perispore line arising from Monascus-like prototype, before 



splitting of archicarp, or from Aspergillaceae. 



4. Pyrenocarp line arising near Monascus-like prototype. Laboul- 



beniales side line near base, and some of the 

 Mycrothyriales as reduced from Sphaeriales. 



5. Discocarp line from Dipodascus-like forms near Monascus, but 



lower (it is not improbable that some of the 

 members of the stock of primitive Euascomy- 

 cetes showed considerable variation in the 

 strength of the ascocarp envelope, also in its 

 presence or absence in forms where it is more or 

 less rudimentary 1 ) ; and some of the Microthy- 

 riales as reduced forms from Phacidiales. 



Or a 6th line also, Laboulbeniales from Monascus-like ancestor. 



1 This variation sometimes occurs in existing forms. Zukal ('89) describes 

 an abnormal case in Eurotium (Aspergillus) herbariorum where the antheridial 

 branch and envelope are wanting, the mass of asci being exposed. In this con- 

 nection it is worthy of note that Fraser and Chambers ('07) regard Aspergillus 

 "as representing a primitive aseomycetous type from which most others can be 

 derived." This suggestion was based on the assumption that the red algae were 

 the ancestors of the sac fungi. On the basis of the counter theory (phyco- 

 mycetous origin) Gymnoascns and Monascus-like forms are more comprehensible 

 as primitive Euascomycetes. 



