Jan. IS. 1920 Further Studies of Sorosporella uvella 42 7 



It should be noted, however, that in some cultures a growth appears 

 such as is shown in Plate 54, B, only to be superseded a few weeks later 

 by one such as is shown in Plate 54, A, which indicates that there is a 

 pronounced tendency on the part of the fungus to change from its natural 

 method of yeastlike development toward a filamentous habit when it is 

 grown on ordinary 2 per cent agar nutrients. "When, however, a very 

 soft agar or a liquid nutrient is employed as a substratum, the normal 

 yeastlike habit has a tendency to persist. 



Under certain other conditions, however, the tendency to produce free 

 elliptical cells followed by mature resting spores has been very pro- 

 nounced, as, for instance, in slanted tubes in which the brainlike, con- 

 voluted type of development has taken place in a number of instances 

 about the point of inoculation, to be followed some weeks later by the 

 formation of grapelike bunches of mature red resting spores near the 

 bottom of the tube where the agar had shrunk away from the glass. 



As noted above, the fungus under consideration was cultivated on a 

 variety of media; and while its development in certain respects was similar 

 on all, differences were observed which are, perhaps, of sufficient worth 

 to be noted. 



POTATO AGAR 



The development of Sorosporella upon potato agar is always feeble; 

 colonies in flasks do not reach a diameter of 4 mm. by the end of two 

 weeks. After a growth of four or five weeks, a dense, prostrate, dirty 

 white surface mycelial weft is formed, which is composed of very fine, 

 hairlike hyphae bearing conidia sparsely. The colony at this time may 

 be I cm. in diameter. In two or three weeks more it reaches a diameter 

 of 2 to 3 cm. and a dark brownish-colored area appears around its pe- 

 riphery. Growth then seems to cease ; the brownish area becomes almost 

 black and extends farther into the medium, forming a dense black ring 

 2 mm. wide around the colony. A microscopic examination of this area 

 in which no surface mycelium can be seen shows that the discoloration 

 is due to a pigmentation of the subsurface mycelium. True resting 

 spores do not form, though the early stages of the Torula-like budding 

 process can be seen. Transfers of the fungus from such cultures to 

 Molisch's agar have shown that the organism is viable after five months. 



molisch's agar 



The composition of Molisch's agar, which has been successfully used for 

 growing many species of fungi, is given on page 423. Sorosporella grows 

 more luxuriantly on it than on any other medium employed, except 

 perhaps beerwort agar. A photograph showing its peculiar gross habit 

 after five weeks growth is given in Plate 54, A. When flasks are inocu- 

 lated by the streak method the fungus may appear in one or both of the 

 two ways that were considered on pages 425-426. Colonies formed by the 



