Entomogbnous Fungi. 443^ 



A culture was started in a half-liter Elirlmeyer flask, having 

 about 4 cm. in depth of potato in small pieces at the bottom. In 

 about two weeks a growth spread over the entire surface. The 

 potato was colored a distinct purple, considerably less intense than 

 in the case of Isaria densa. After about 20 days the entire sui'face 

 became marked with a creamy-white covering composed of conidia. 

 In many places there appeared crowded radiating growths of 

 threads, spherical in form, having a creamy-white color and a vel- 

 vety appearance. The buff color is usuall)- more pronounced at the 

 base and center of such spherical growths ; the growth is also more 

 dense at these places. In Ave or six days more the velvety pile col- 

 lapses gradually, and from 3 to 15 cylindrical processes are produced 

 in its place. These present a color more intensely creamy than 

 the velvet balls from which they spring. The cylindrical sporo- 

 phores seem to protrude through the sphere at the same time that 

 the pile collapses. They develop into long, slender, erect and usually 

 clavate sporophores, generally simple though sometimes branched. 

 They occasionally reach the length of 2^ cm. The color of the 

 mycelium, where it touches the glass, is orange. These characters 

 show this form to be an Isaria, and the name Isaria vexans is here 

 proposed for it. 



This method of growing fungi in flasks, allows the fungus to 

 reach a maturity that is impossible in the smaller tubes, because of 

 the insuflicient supply of moisture and nutriment. 



Infection experiments were made with four species of insects. 

 Twenty-four larva3 of our common cabbage-butterflj', Pieris rapcBy 

 were dusted with conidia obtained from a potato culture. After 

 five days, four of the larva? were dead, and colored a deep vina- 

 ceous purple. In places were patches of a white felty growth of 

 the mycelium. After five days more, the remainder of the larvae 

 had pupated, excepting one which soon died. After seven days 

 more, three out of the original twenty -four emerged, all the rest 

 having succumbed. In the case of pupte, the disease invariably 

 starts from the wing-pads. Its presence is indicated by a deep 

 purple color which spreads from the wing-pads over the entire 

 body. This purple color is also noted by Professor Forbes * who 

 finds cabbage-worms are turned purple when attacked by the 

 fungus used against the chinch-bug. The death of the insect may 



' Bull. No. 38, Ag. Exp. Sta. of the Univ. of 111., 1895, p. 33 aud 43-44. 



