THE FUNGI WHICH CAUSE PLANT DISEASE 165 



to the Endomycetacese; the forms with a more highly developed 

 peridium, to the Pyrenomycetes, particularly to the Perisporiales. 

 Conidial forms are usually present, indeed in many cases they 

 preponderate almost to the entire exclusion of the ascigerous form 

 which may be seen only under very exceptional conditions. 



Sexual reproduction has been demonstrated in several families. 

 In the Gymnoascaceae (Dale ^* and Eidam ^) there are usually two 

 twisted branches (Fig. 118) which conjugate. These branches 

 are multinucleate at the time of fusion. The ascogonium de- 

 velops from this fertiUzation much as is described on pages 116- 

 117. In the Aspergillaceae similar sexual organs are formed but 

 parthenogenesis or a much reduced form of fertilization is often 

 met. In all, the species number two hundred fifty or more. 



Key to Families of Aspergillales 



Peridium made up of loose floccose hyphse. 1. Gymnoascaceae. 

 Peridium compact, closed 

 Ascocarps mostly small, not subterranean 

 Ascocarps mostly sessile without 



stroma; peridia remaining closed. . 2. Aspergillacese, p. 166. 

 Ascocarps mostly stalked; peridia open- 

 ing at maturity by lobes, or ir- 

 regularly 3. Onygenacese. 



Ascocarps sessile, the spores issue in 

 columnar masses from the goblet- 

 shaped peridia 4. Trichocomacea. 



Ascocarps sessile on a small stroma. . . 5. Myriangiacea, p. 170. 

 Ascocarps mostly enlarged, tuberous, sub- 

 terranean. 

 Peridium clearly distinct from the 

 walls of the ascocarp; spore masses 



powdery at maturity 6. Elaphomycetaceffi. 



Peridium not clearly limited, continu- 

 ous with the walls of the ascocarp; 

 spore masses never powdery 7. Terf eziacea. 



Of these the second and fifth families only contain pathogens. 

 The Gymnoascaceae of five genera and some fifteen species are 

 foimd on manure, and other organic matter. The third and fourth 



