"BLACK YEASTS" 111 



green colony with a velvety surface. The reverse of the colony is 

 almost black. The same mold is found from platings of soil, espe- 

 cially soil with an abundance of decomposing plant residues. These 

 are found most frequently to be organisms designated as Clado- 

 sporiwn herbarum or H ormodendrum cladosporoides. Cladosporium 

 and Hormodendrum have been separated on the basis of production 

 of two-celled as opposed to one-celled conidia. However, the bi- 

 cellular conidia usually do not develop until late, unicellular spores 

 forming first, and cultures which are regularly one-celled may occa- 

 sionally show a few two-celled spores. It is usually agreed that 

 there is but one genus and species may or may 

 not develop two-celled spores. Since Clado- 

 sporium has priority, this name should be used 

 and Hormodendrum reduced to synonymy.^* 

 One species of Cladosporium is the imperfect 

 form of an Ascomycete, MycosphaereUa Tulas- 

 nei, which is parasitic on various plants. 



In Cladosporium the conidia are formed dif- 

 ferently than in molds like Aspergillus and 



Penicillium. In these molds the conidia are -n ^o o u j 



iiG. 63. Spore head 



formed by a constriction of the tip of the ste- ^f Cladosporium. 



rigma, which then forms a second spore that 

 pushes the first one ahead of it, and so on ; thus the terminal spore of 

 a chain is the oldest and frequently the largest. In Cladosporium, 

 however, after the first spores have formed on the conidiophore they 

 bud to form secondary spores and no further conidia are formed 

 directly by the conidiophore. Then only the terminal spores bud 

 and in the chains thus formed the youngest, and frequently the 

 smallest, spores are found at the ends of the chains. Moreover a 

 spore may develop more than one new spore by forming more than 

 one bud and thus we find that the chains of conidia are branched 

 (Fig. 63). 



These molds are found, as was stated, in soil, and they are also 

 found in large number on decaying leaves, straw, and other vegeta- 

 tion on the surface of the soil. They are said to be of some impor- 

 tance in the spoilage of malt and of stored tobacco. From time to 

 time members of this group are reported as causes of superficial skin 

 lesions in man without clear evidence of their pathogenicity. For 

 relationship of Cladosporium to chromoblastomycosis, see page 199. 



"Black Yeasts," "Torula nigra," "Monilia nigra." There has 

 been described from time to time a series of yeasts or yeast-like 

 organisms which produce a characteristic black color. They have 



