14 Minnesota Plant Diseases. 



be made by the plant to produce reproductive bodies and then 

 one grand effort is made. A single mushroom may produce mil- 

 lions of spores and shed them all in a single day. Not all para- 

 sites, however, are small; but in some cases, as in the wound 

 parasites, they may produce large shelf-like fruiting bodies. 

 These plants are often saprophytic at first, becoming parasitic 

 later. 



Storage organs. Most fungi use the food materials which 

 have been absorbed from their various sources, for the immedi- 

 ate production of fruiting bodies. Consequently the fungus con- 

 sists almost entirely of these two regions, the absorptive myce- 



FIG. 4. Storage organ of a cup fungus (Sclerotinia) with fruiting bodies 

 (stalked cups) which have grown from the storage organs. Original. 



lium and the reproductive organs. Some fungi, however, have 

 learned to store food for future use and are thus able to collect 

 considerable material, before attempting the formation of 

 spore-bearing organs. The ergot of rye is such a storage or- 

 gan, formed by a fungus parasitic on the rye. The fungus ap- 

 propriates the nutrient material of the young grain and builds 

 up a solid elongated or roundish body which, when mature, be- 

 comes dark violet colored or blackish. This body is composed 

 of parallel threads of the fungus tightly compacted together and 



