MOLDS 



57 



CLADOSPORIUM (AND HORMODENDRON). The species of Cladospor- 

 ium occur frequently in cultures of decaying vegetable matter, of milk 

 and cream, or butter. The colonies liquefy gelatin. Both mycelium 

 and spores are at first colorless, but later dark colored to almost black, 

 with spores becoming two-celled in very old cultures. 



- Cladosporium herbarum is the commonest species encountered.* 

 Colonies in culture media differ so greatly in structure from those upon 

 natural substrata as to make identification of species questionable. 

 (Fig. 37). Much confusion is therefore found in the use of the names 

 of species of Cladosporium and the related genus, Hormodendron, which 

 is separated by some. 



FIG. 37. FIG. 38. FIG. 39. 



FIG. 37. Cladosporium herbarum, showing the forms of conidiophores and conidia 

 which are very common upon laboratory culture media. (Original.) 



FIG. 38. Spores of Alternaria sp. (Original.) 



FIG. 39. Fusarium from decaying potato, a, Spores showing curvature and 

 septa; b, germination of spores; c, development of spores in petri-dish culture; d, 

 mass of spores as found in culture. (Original.) 



ALTERNARIA AND FUSARIUM. The frequent occurrence of species of 

 Alternaria and Fusarium in cultures demands that the generic characters 

 be recognized. Both, as a rule, produce abundant growth with a tend- 

 ency to over-run cultures of other forms (Figs. 38, 39). The spores of 

 Alternaria are brown, Indian-club form or muriform (divided into 

 several cells by longitudinal as well as cross walls), and are connected 

 together into chains (Fig. 38). The spores of Fusarium are colorless, 

 either straight, sickle-shaped, or crescent-shaped, divided into several 

 cells by cross walls, are produced in chains or adhere into masses on the 

 tips of the fertile branchlets. The morphology of colonies in culture 

 varies widely from the descriptions of the same species under natural 

 conditions. Species of Fusarium frequently produce bright colors in 



* This species has been shown to be a conidial form of Spaerella tulasnei Janczewski, but the 

 bacteriological student will meet only the conidial stage. 



