426 Journal of Agricultural Research Voi. xvni, No. s 



spherical in form and give rise to other cells of the same nature by a pro- 

 liferating process, ultimately resulting in a growth of the type illustrated 

 in Plate 51,8. Again, under conditions not fully understood, the ele- 

 ments of such a proliferating colony may become largely disassociated 

 and reproduce by a yeastlike budding process. When either of the last 

 two methods of development is followed the cells normally round up and 

 become thick-walled, forming bodies that have been called resting spores. 

 These bodies are homologous to those found in diseased cutworms and 

 resemble them in the distinctive red color which is visible to the naked 

 eye. On account of the fact, however, that the cells which are differ- 

 entiated to form resting spores may germinate prematurely in culture 

 and to the fact that the red color is associated only with mature, thick- 

 walled chlamydospores, it should be stated that such pigmentation is not 

 always apparent, or it may appear in limited areas in a culture and not 

 be present elsewhere. 



As a result of these diverse methods of development, cultures are 

 produced which to the naked eye present quite different appearances, 

 differences that seem to be due entirely to the tendency of the chlamy- 

 dospores to germinate in situ at any time during the process of their 

 formation. A comparison of Plate 54, B, with Plate 54, A, will illus- 

 trate such different types of growth; and while these photographs are 

 from cultures on beerwort agar and Molisch agar, respectively, dissim- 

 ilarity is often just as apparent in the same culture. The thallus shown 

 in the latter is convoluted, creamy white, and woolly. It is composed for 

 the most part of immature resting spores which have germinated in situ 

 and have remained attached to one another. In such a proliferating 

 process of growth, if new cells, whether produced laterally or terminally, 

 remain attached to their parents and are incompletely abstricted, a 

 toruloid growth results, the older cells of which germinate in situ before 

 they are matured, forming sterigmata and conidia. When several 

 closely opposed colonies develop in this manner, a thallus is formed 

 which resembles that illustrated in Plate 54, A. 



If, on the other hand, the new cells which are formed become largely 

 disassociated from their parents, a growth results that is somewhat 

 different in gross appearance. Under such conditions growth is typically 

 yeastlike, and the elliptical detached cells enlarge considerably by the 

 absorption of nourishment and bud off new cells, so that eventually 

 heaped-up, grapelike bunches are formed. Continued swelling renders 

 the cells nearly spherical in form. Thick walls are deposited. When 

 viewed with the naked eye the characteristic red color invariably asso- 

 ciated with fully formed resting spores is at once apparent. Plate 54, B, 

 will illustrate the type of thallus that results from such a m.ethod of de- 

 velopment, although the photograph was taken a few days too late to 

 show it to the best advantage because germination of the resting spores 

 had already begun in the older portions of the culture. 



