Jan. IS. 1920 Further Studies of Sorosporella uvella 409 



To determine whether or not fresh larvae could be infected with newly- 

 formed ungerminated resting spores, 10 cutworms were allowed to crawl 

 over and were rolled about in a finely powdered layer of chlamydospores 

 in a Petri dish for 15 minutes on June 7, 191 7, after which they were 

 removed to sterile dishes in which there was a small amount of sterile 

 moist sand. By June 25 six of the larv^as had pupated, afterward emerg- 

 ing. One died, but apparently not from the Sorosporella disease. On 

 June 20 the fungus was discovered in one dead pupa, and on July 2 in 

 another. One insect escaped during the feeding interval following 

 inoculation. Since the larvae were placed after inoculation in a sterile 

 covered dish, the cover of which was removed only when fresh food 

 was inserted, the possibility of infection from other sources seems rather 

 remote. Although a low percentage (2 per cent) of the larvae died from 

 the disease, it should be noted that the deaths occurred on the twenty- 

 third and twenty-fifth days after inoculation, whereas the normal incuba- 

 tion period is from 10 to 12 days, as will be shown later. As will be 

 explained below, there occurs within the blood of infected cutworms a 

 phagocytic reaction which may have inhibited the development of the 

 disease, thus tending to protract the incubation period; but it seems 

 more reasonable to believe in the present instance that infection was 

 secured, not through the resting spores directly, but by conidia which 

 they produced after germination; and it is obvious that the period of 

 time necessary for the germination of the resting spores and for the pro- 

 duction of conidia which may or may not have been in position to infect 

 lar\^ae immediately after formation would readily conform with the re- 

 sults of the test. 



Several important facts become apparent as a result of such tests, 

 some of which appear to have a definite economic bearing. It has been 

 shown that the chlamydospores are formed for the purpose of tiding the 

 fungus over unfavorable conditions, since they are thick-walled and are 

 able successfully to withstand desiccation as well as out-of-door winter 

 temperatures. Furthermore, upon germination in hanging drops of 

 water or in a moist chamber, they do not produce simple undifferenti- 

 ated germ tubes as would be expected under these conditions, but 

 complexed branching conidiophores, which in turn give rise to thin-walled 

 conidia. 



Although the primary function of the resting spores is that described 

 above, it has been shown that such bodies do not necessarily require a 

 long period of rest but may germinate soon after their formation if freely 

 exposed to moist air. In this respect they are similar to the spores of 

 the Ustilaginales and to the bulbils. 



It is reasonable to conclude, therefore, that several generations of the 

 fungus may occur during one season under field conditions in spite of the 

 fact that resting spores exclusively are formed at the close of the vegeta- 

 tive development of the organism. This is all the more probable 



