Minnesota Plant Diseases. 



131 



parts of the insect-body, build up a mycelium which consumes 

 all of the interior of the host except the chitinous skin. It 

 thus stores up an enormous amount of nutrient material in the 

 form of a storage organ or sclerotium, which is an exact cast, 

 not only of the external form of the insect but also of the in- 

 ternal organs. When this storage organ has rested for some 

 time, and when conditions of moisture and temperature are 

 favorable, it sends up, 

 usually one or more, 

 rarely two, stalks, 

 which come above 

 ground. Here they 

 form a club-s ha p e d, 

 bright-orange - colored 

 body which may easily 

 be mistaken for a club 

 Close exam- 

 shows this 

 contain nu- 

 small holes 

 just as in the head of 

 the stalk on the germi- 

 nating ergot, and these 

 holes again communi- 

 cate with pear-shaped 

 cavities, which are the 

 s p o r e-sac capsules. 

 The sacs also contain 

 eight long, thread- 

 shaped spores, divided 

 into numerous cells, 

 each of which is able to form a germ thread and thus infect 

 other grubs or caterpillars. Sometimes the storage organ 

 does not produce a sac-capsule-bearing stalk, but produces in 

 one of several ways a great abundance of accessory spore forms 

 which are pinched off from threads in enormous numbers. 

 This happens if one places a freshly developed storage organ 

 in a moist chamber, or it may happen in nature where one 

 finds frayed-out branches or strands from the storage organ 



fungus, 

 ination 

 body to 

 merous 



Fig. 56. — A caterpillar tungus. The insect-shaped 

 bodies are fungus casts of threads which form a 

 storage organ; raising from these are club-shaped 

 bodies which are covered above with fine warts. 

 These warts are the tops of the sac-spore-capsules. 

 Original. 



