XI, B, 6 Wade: Cultivation of a Pathogenic Fungits 275 



After several days the aerial growth for the most part collap- 

 ses and the surface appears dry and dusty over a compact, firm 

 surface layer. The agar itself becomes gradually clouded by 

 down growth of the mycelium and assumes a yellow to light 

 brown tint. 



In fluid media. — In the depths of ordinary bouillon the fungus 

 grows in loose, flocculent masses. In glycerin bouillon, whether 

 0.5 or 10.0 per cent, the growth is very slow, occurs in much 

 smaller, more compact white masses than in other bouillons, and 

 is always deep in the medium. 



In most fluid cultures the greater part of the growth is on 

 the surface where, in a few days, a thick pellicle is formed. 

 The upper surface is at first deeply covered with fine aerial 

 hyphse which, as on agar, soon collapse (fig. 40). In a few 

 weeks the bouillon assumes a deep amber color. 



Growth is by far most abundant on banana bouillon with or 

 without glycerin (fig. 39). The layer is firm, the under surface 

 is smooth, and when torn there appears below the superficial 

 mycelium a distinct membrane, about 1 millimeter thick, which 

 is sharply demarked, firm, homogeneous, and yellow. 



Growth is markedly greater at room than at incubator tem- 

 perature. Anaerobiasis is also very unfavorable to active 

 growth, often inhibiting it completely. 



MORPHOLOGY OF MYCELIAL FORM 



On solid media. — In the rapidly growing cultures the young 

 hyphae are rather thin and long and are branched at rather 

 infrequent intervals. Septation is seen only in old filaments (fig. 

 43) . In the aerial hyphse vacuoles develop (fig. 41) , and the pro- 

 toplasm is reduced to narrow transverse bands somewhat sug- 

 gestive of septa which determine the points at which the filament 

 separates into individual cells. This process of maturation and 

 dissociation may be complete in two or three days. 



In the separated elements, as in figs. 34 and 35, there sometimes 

 is evident a tendency to polar accumulation of the protoplasm. 

 Hyaline granules often appear, and large and small meta- 

 chromatic granules are common. After a time some of these 

 entire segments become hyaline (fig. 42). 



Upon transplanting these elements to fresh media, develop- 

 ment usually begins within three or four hours by a lateral 

 pseudopodic offshoot. Sometimes two and, rarely, three of 

 these develop from, a single mother cell, which becomes vacuo- 

 lated and remains (as in figs. 41 and 42) in direct connection 

 with the growing hyphae. 



