Minnesota Plant Diseases. 129 



Now it is only in the young stages of the flower that these 

 spores can attack the grain so that rapid spread of spores is 

 necessary and is, moreover, readily accomplished by this insect- 

 method of spore distribution. These spores are produced by 

 the fungus for some time. Toward the time of ripening of the 

 grain, the production of summer spores ceases and the fungus 

 commences to pack up reserve nutrition in its threads. These 

 are now compacted together in a very solid mass the exterior 

 of which turns violet black. The whole structure becomes a 

 storage organ or sclerotium, and often requires a rest period be- 

 fore it will develop further. In this sclerotium nutrient mate- 

 rial is found in the form of fungus starch and oils. Certain vio- 

 lent poisons are also found in them and are extensively used in 

 medicine, for this storage organ is known in pharmacy as the 

 drug "ergot." Of just what use to the fungus these poisonous 

 compounds are is not quite clear. Possibly they tend to pre- 

 vent the consumption of strongly ergotized grains, thus avoid- 

 ing destruction by feeding animals. 



In the spring time, after their winter rest, the ergots are 

 capable of further growth. When placed in proper conditions 

 of moisture and temperature they send out small cylindrical 

 stalks which bear tiny spherical heads about the size of small 

 brown mustard seeds. These little heads become blackish 

 in color and bear the sac spores. They are not, however, single 

 sac-capsules but, if one examines the surface of this sphere, one 

 finds a large number of little openings and. upon further inves- 

 tigation, these openings are seen to connect with pear-shaped 

 cavities just beneath the surface. Each of these cavities is in 

 reality a spore-sac capsule. In other words, the spore-sac cap- 

 sules have been aggregated together onto a common surface 

 and produced in abundance on account of the great amount of 

 available storage material in the ergot. In each sac capsule 

 are numerous very long, cylindrical sacs, and each sac contains 

 eight long thread-like spores, which have already been divid- 

 ed by cross-walls into about sixty-four cells. These cells sepa- 

 rate very readily and each is capable of growing out into a my- 

 celium, so that each sac contains about five hundred spore cells. 

 In addition to the spore-sacs there may be long, swollen 

 threads in the sac-capsule, which aid especially in discharging 



