Minnesota Plant Diseases. 



" / 



pests such a fungus may become an efficient aid to the horti- 

 culturist. The method of attack of this fungus is a very un- 

 usual one. The mycelium is built on the principle of a net in 

 which the threads of the fungus form loops or meshes. In 

 these meshes the wiggling pin worm becomes entangled and 

 every effort to free itself usually results in a securer imprison- 

 ment. When the worm is held fast the fungus sends out 

 threads which penetrate the body of the prisoner and absorb 

 its substance. 



Amongst the true worms, fungi have been reported on 

 the common earth worm. These fungi belong to the fish or 

 water molds. The little water flea (Daphne) is the host of a 

 very interesting fungus. This fungus is said to be a relative 

 of the yeast fungi which are not, as a rule, parasites, but true 

 saprophytes. The spores of this yeast or yeast-like plant are 

 long, pointed, almost needle-shaped, and when taken into the 

 alimentary canal of the water daphne they penetrate the wall 

 of the canal and get into the body cavity. Here a fight ensues 

 between the white corpuscles and the spores. If the latter con- 

 quer they soon commence to divide in yeast fashion and rapidly 

 use up the nutrition derived from the fluid of the body cavity. 

 The host animal soon becomes sluggish and dies. Later the 

 needle-shaped spores are again set free and may be swallowed 

 by other daphnes. 



The crabs have also been reported as hosts for fungi, but 

 such occurrences have not been very frequently noted. The 

 parasites in these cases are water or fish molds. Amongst the 

 spiders a black fungus parasite is known. Even upon the clam 

 fungi have been reported, but their parasitic nature has not yet 

 been proven. Shell-boring fungi are often found on the shells 

 of such animals. 



Diseases of insects. Of all the animals the insects are by 

 far the most popular hosts for parasitic fungi. Most of the 

 fungus parasites attack the insects in their larval stages, when 

 the latter, with worm-like habits, crawl through the soil or in 

 other moist places. Hence the fungi most frequent upon them 

 are forms of the algal fungi which are also typically aquatic in 

 habit, though of course many have learned to live in dry situ- 

 ations. The fungi of insects have certain advantages. In the 



