200 AGRICULTURAL EXPERIMENT STATION. [Jan. 



I. Slime Moulds (Myxomycetes) . — See above, p. 201. 



II. Bacteria {Schizomycetes) . — See above, p. 201. 



III. Fungi. — These may be conveniently divided, for 

 our purpose, into about seventeen groups, all but the last 

 composed of quite closely related plants, as follows : — 



1. Downy mildews and white rusts (^Peronosporem) are 

 internal parasites in the herbaceous parts of plants. Most 

 of them produce summer spores, on threads which break 

 through the surface of the plant into the air ; and resting 

 spores, in the interior of the host. The latter are set free 

 by the decay, during the winter, of the tissues in which 

 they are imbedded, and then germinate in spring. The 

 former are scattered by the currents of air, and rapidly 

 infect new hosts. 



Among diseases caused by attacks of members of this 

 group of fungi are the potato rot, downy mildews of the 

 grape, lettuce, onion, etc., and " damping off ' of seedlings. 



2. Water moulds (^8aprolegniacecie) are chiefly saprophytes 

 on animal substances (dead insects, etc.) in water; but one 

 of them can attack living fish, notably the salmon, destroy- 

 ing the skin, commonly of the head region, by its gradual 

 spread, and finally killing its victim. 



3. Leaf-g all fungi (^Chytridiacem) are very small and 

 simple parasites, some of which form pustule-like swellings 

 of herbaceous parts of flowering plants, and so merit the 

 name here given. A majority of the members of the group, 

 however, are parasites on the lower water plants, and of no 

 present interest. 



4. True moulds (Mucorini) comprise fungi which are 

 saprophytes on common vegetable substances, and others 

 which are parasites on the mycelia of the former. They are 

 of no special interest in the present connection. 



5. Insect fungi {EntomojjJtthoreoi) are nearly all parasites 

 of insects, and cause the death of their hosts. Their only 

 economic interest is in the possibility which has been 

 suggested that they may be artificially propagated for use in 

 destroying insect pests. The clieme however is one of 

 very doubtful practicalnlity. 



6. Smuts ( Ustilaginece) are internal parasites of flower- 

 ing plants, and develop both mycelium and spores in the 



