106 MISSOURI BOTANICAL GAKDEN. 



small, white patch on the surface. In two or three days, 

 sporophores are thrown up from the prostrate mycelium. 

 These bear branching hyphae which form terminally by 

 abstriction, simple, continuous chains of conidia. This 

 portion of the colony is usualbygray to blue green in color, 

 varying with the medium. The filaments of the mycelium 

 in rich agar media often bear swollen cells, resembling 

 chlamydospores in shape (pi. 11, f. 2), but which have 

 not been observed to form the thicker wall, characteristic 

 of such spores. Under the same condition, the mycelium 

 becomes fluffy, and many filaments unite together in 

 strands, forming Coremium clusters. The filaments ordi- 

 narily measure 3/j, to 4//, in diameter, and contain elongated 

 cells. On the other hand, the swollen cells are spherical, 

 with a diameter of 4/x to S/x. 



Upon older cultures, especially upon wood, there are 

 formed rounded tufts or clumps of curled and distorted 

 hyphae and filaments, which are either lemon-yellow or 

 orange-red in color, varying with the acidity or alkalinity of 

 the culture medium. The color is due to the secretion of 

 a pigment in the form of granules on the surface of the fil- 

 ament, evidently by exudation (pi. 11, f. 3). This pig- 

 ment is readily soluble in slightly acid or alkaline water, 

 in hot alcohol, and in some other solvents. It is red when 

 alkaline and yellow when acid. The fungus, as a rule, 

 when grown artificially, overcomes a moderate amount of 

 alkalinity by the formation of an acid, and as a result, 

 most cultures assume the lemon-yellow color when old. In 

 cultures on wood, especially sapwood, the pigment is car- 

 ried into the wood cavities by absorption, thus staining the 

 wood. The color, although bright at first, fades as the 

 culture grows old and dries out. 



Conidia. 



The conidia are borne on conidiophores which vary in 

 length from UJOfi to 500/x, with a diameter of 3/*, or slight- 



