EUASCOMYCETES 



175 



bean, assists in the preparation of the soy bean as used in Java; several 

 species of Citromyces are used in citric acid fermentation; Penicillium 

 roqueforti and P. camemberti lend to the corresponding cheeses their 

 characteristic aroma and consistency. Some species whose optimal 

 temperature is about 37° are pathogenic to animals and cause mycoses; 

 Aspergillus fumigatus and A. flavus grow in the human ear and the former 

 causes most of the cases diagnosed as tuberculosis, in which Myco- 

 bacterium tuberculosis is not found. Still other species are plant path- 

 ogens, thus P. italicum and P. digitatum (P. olivaceum) cause decay of 

 ripe southern fruits, and A. niger is said to be parasitic in dates and 

 make them unpalatable by fermentation of the starch. 



The thallus is formed as in the previous groups. It is generally color- 

 less; in some species the hyphae may form in the interior of the cells 



Fig. 109. — Aspergillus herbariorum. Development of conidiophore. (X600; after 



Dangeard, 1907.) 



a yellow to red, rarely green, color which later diffuses through the cell 

 membrane and passes out into the nutritive solution. Exceptionally, 

 as in P. camemberti and some Acaulium sp., the hyphae may break up 

 into oidia or, again in Acaulium sp., form gemmae or, as in Aspergillus 

 niger or A. Oryzae (Schramm, 1914; Zikes, 1922), develop sprout mycelia. 

 The hyphae form an arachnoid cover over the substrate and interwine 

 rapidly into a dense mat or crust. This is generally white at first and 

 after a few days attains its characteristic color from its conidia. 



As imperfect forms, in addition to the above-mentioned oidia, only 

 conidiophores and conidia have been known. The conidiophores arise 

 only on the mycelium of the upper surface as vertical, projecting, aerial 

 hyphae. In the simplest case, as in Aspergillus, they are unbranched; 

 as in Sy?icephalastrum among the Mucoraceae, their ends swell capitately 

 and allow the majority of the nuclei to come out into short flask-shaped 

 phialides (sterigmata) which cut off successively a chain of multinu- 

 cleate conidia (Fig. 109). While in the typical species of Aspergillus, 

 the phialides are unbranched (Fig. 114, A), in the subgenus Sterigmato- 



