Jan. IS, 1920 Further Studies of Sorosporella wvella 425 



the organism, but although a limited amount of air seems to be required, 

 free circulation of air is not necessary, because, as noted above, blasto- 

 cysts were found to develop in fermentation tubes at some distance 

 below the surface of the nutrient solution. 



To grow the fungus in an atmosphere of nitrogen instead of air, 

 Buchner's method was employed. Small test tubes filled with Molisch's 

 solution and inoculated were placed in larger test tubes, the latter 

 having been previously filled to a depth of i cm. with pyrogallic acid. A 

 few cubic centimeters of a strong solution of caustic soda were then 

 poured quickly between the tubes, the larger of which was immediately 

 sealed with a rubber stopper. The action of the caustic soda upon the 

 pyrogallic acid renders the latter alkaline and in so doing extracts the 

 oxygen from the air, leaving an atmosphere that is composed largely of 

 nitrogen. 



When subjected to the conditions outlined above, Sorosporella ex- 

 hibited no signs of growth whatever; and it may be concluded, there- 

 fore, that an atmosphere of nitrogen inhibits growth. 



Upon a favorable nutrient and when subjected to the usual cultural 

 conditions in the laboratory, the development of the fungus under con- 

 sideration takes place somewhat as follows : Mature resting spores when 

 sown either in Van Tiegham cells or in Petri dishes may give rise di- 

 rectly to conidiophores and conidia, as in a drop of water (PI. 51, L); 

 or at times vegetative, budlike outgrowths are produced, such as are 

 shown at the bottom of M in Plate 51. Such budlike processes produce 

 enormous numbers of cells that remain attached to one another and 

 form a colony. After a short period the members of this colony round 

 up and then give rise to conidiophores and conidia. The conidia, how- 

 ever, when sown on nutrient agar, put forth slender germ tubes (PI. 51, 

 Q), which after a time become septate and branch profusely. In about 

 10 days a colony is formed, in which, in addition to such slender hyphae, 

 there can also be detected large, thick, many-septate fungus filaments, 

 the cells of which are more or less barrel-shaped. In young cultures it 

 can readily be determined that such hyphse arise as branches of the slen- 

 der threads. An examination of a colony 2 weeks after the conidia are 

 sown will show, therefore, two types of filaments which are so thor- 

 oughly intermingled that it is impossible to ascertain the origin of 

 either. Many of the slender hyphae increase greatly in length, and those 

 which are at or near the surface of the nutrient agar give rise to sterig- 

 mata of the type illustrated in PI. 52, O. Usually the sterigmata are 

 sessile and occur irregularly on the prostrate hyphae, which often show 

 a tendency to group themselves in bundles. Occasionally upright, much- 

 branched conidiophores are produced of a type quite similar to those 

 arising from the germinating resting spores. 



The thick barrel-shaped cells, however, although at times giving rise to 

 slender, prostrate, vegetative filaments, usually grow more nearly 



