114 



THE FUNGI IMPERFECT! AND THE ASCOMYCETES 



cells. These conidia occur in chains, sometimes with short stretches 

 of mycelium between the spores. There are a number of species, 

 many of which are plant pathogens. Stemphyllium is a closely re- 

 lated genus. For a discussion of both genera, consult the articles by 

 Groves and Skolko.^ 



Species of Alternaria have been found growing in pus of super- 

 ficial wounds, and it has been suggested that they have some patho- 



FiG. 66. Conidia of Alternaria. 



genie action. But this is probably not true, because the organisms 

 may be growing merely as saprophytes upon the pus, or more likely 

 upon the cellulose 'of the dressings. Their relation to asthma is 

 mentioned on page 136. 



Helminthosporium. Next to Cladosporium and Alternaria, prob- 

 ably the most common dematiaceous mold encountered by the bac- 

 teriologist is Helminthosporium. The conidiophores usually arise 

 in groups and are unbranched and septate in most cases. The conidia 

 are large, elongate, and cylindrical or ovate. The ends of the 

 conidia may be rounded or pointed. Many, usually more than four, 

 crosswalls are found in each conidium, which is very dark in color. 

 Curvularia is a related genus. See Fig. 67. 



