36 VARIATIONS IN THE LOWER FUNGI 



described as woolly degeneration. This woolly degeneration occurs 

 not only with the ringworm fungi, but also with a variety of molds, 

 such as Aspergillus nidulans, which loses first the ability to form 

 perithecia, and then forms fewer and fewer conidia and more and 

 more sterile mycelium. It is most likely to occur when cultures are 

 frequently transferred on highly favorable media. This fact was 

 recognized long ago by Sabouraud who devised a conservation me- 

 dium, rich in peptone and poor in sugar, on which stock cultures 

 were maintained. These should be transferred only at long intervals. 



Another type of change observed in cultures of fungi has been 

 called faviform degeneration by Alexander.^ In ringworm fungi it 

 usually follows a stage of woolly degeneration. The mold now grows 

 as a low, fiat, wrinkled, waxy-looking mass of mycelium, without any 

 aerial mycelium or conidia, firmly adherent to the agar. This is the 

 normal appearance of the fungus of favus, hence the name. Although 

 less frequently observed than woolly degeneration, it is seen in a 

 variety of molds, and occurs very constantly with the organism of 

 North American blastomycosis, a fungus which normally grows with 

 an abundance of sterile woolly aerial mycelium. 



Still another type of change may be observed in certain fungi 

 which normally do not produce any aerial mycelium, but grow as a 

 moist mat on the surface of the agar. Such fungi are Candida Krusei, 

 Sporofrichiwi Schenckii, and Pullularia pidlidans. I have observed 

 with all of these, after long-continued cultivation on Sabouraud agar, 

 the development of dry aerial mycelium, with conidia in the last two. 



Finally, one may observe changes in yeasts after long-continued 

 cultivation. Normally forming no mycelium, they may develop first 

 elongated cells, then pseudomycelium, and finally some filaments of 

 true, septate, branched mycelium. An extension of this phenomenon 

 is observed in organisms like C. albicans, which on Sabouraud agar 

 normally form an abundance of yeast cells and little mycelium, but 

 which on long-continued cultivation gradually produce more and 

 more mycelium and fewer yeast cells, so that eventually they come 

 to look like C. Krusei. 



Microbic Dissociation in Fungi. It may be observed that all these 

 variations form a continuous series which may be indicated thus: 



Yeast -^ Submerged -» Aerial -^ Sterile -> Faviform 

 mycelium mycelium woolly growth 



with aerial 



spores mycelium 



-So far as I know, no single fungus has ever been observed to go 

 through all these changes, unless possibly Blastomyces dermatitidis, 



