41 o Journal of Agricultural Research voi. xvm. no. s 



because most species of cutworms habitually burrow in the soil, where 

 they come in contact with the conidia, and because the generations of 

 different species and even of the same species overlap and are suscepti- 

 ble to the disease as has been shown by inoculation experiments. 



The results of the test with the army worm pupae indicate, however, 

 that when the resting spores are formed and retained in a thick, intact, 

 resistant, chitinous wall such as the insect forms at this period, germi- 

 nation will not take place; and in fact development of conidiophores is 

 much less luxuriant upon the untorn body wall of a larva, which, how- 

 ever, becomes very thin and parchment-like after a time, than on one 

 which has been torn open. This difference is well shown on Plate 5 1 , K, 

 and Plate 55, A. 



It is, therefore, apparent that although the germ tubes have the 

 power of breaking out through very thin chitin, the process of germina- 

 tion is undoubtedly facilitated greatly when larvae become disintegrated 

 in the soil. 



The conidia which are borne at the tips of the germ tubes are, as stated 

 above, of a different nature from the resting spores. Their thinner walls 

 and formation aerially in enormous numbers, as well as their general 

 ephemeral appearance, indicate that, like analogous conidia of other 

 Hyphomycetes, their function, quite unlike that of the resting spores, is 

 to spread the organism rapidly and as completely as possible while 

 favorable conditions obtain. 



In a water drop, or in a drop of nutrient agar in Van Tiegham cells, 

 germination of the conidia takes place as shown on Plate 51, J, by the 

 production of threadlike, sinuous germ tubes. Experiments have shown 

 (P- 433) that when conidia are placed in contact with healthy insects, 

 either externally or internally, infection may be readily induced; and it 

 is probable that germ tubes similar to those mentioned above penetrate 

 the thinner portions of the body wall from without, or from within 

 through the intestine, producing at their tips bodies which give rise to 

 yeastlike vegetative cells. The exact method of infection, however, has 

 not been determined, in spite of the fact that a large number of insects 

 have been killed, fixed, and sectioned in attempts to observ^e germ tubes 

 actually penetrating the insect tissues. 



In the foregoing discussion the morphology of the single-walled resting 

 spores as well as their functions and germination has been considered. 

 It has been shown that they produce conidiophores, which in turn pro- 

 duce the thin-walled conidia. The production of conidia evidently 

 marks the termination of the reproductive stage, all phases of which 

 occur after the death of the host. The remaining stages, except the for- 

 mation of the chlamydospores, are vegetative in nature and are found 

 within the living insects after infection. 



Cutworms parasitized by Sorosporella uvella, like insects attacked by 

 other fungous parasites, exhibit no symptoms of disease during the 



