INSECTS, FUNGI, PLANT DISEASES, ETC. 



153 



applications of vermicides, it is therefore recommended 

 to sterilize the soil by starvation of the worm — that is, 

 planting only those plants which are known to be free 

 from the attacks — and by clean 

 cultivation. 



PLANT DISEASES. 



These diseases are referred to 

 what are called fungi, which be- 

 long to the Cryptogamic branch 

 of the vegetable kingdom. A 

 fungus is a plant that is devoid of 

 the coloring matter or chloro- 

 phyll so necessary in the higher 

 plants for a proper assimilation 

 of the crude food. This coloring 

 matter being absent in the body 

 of the fungus, it becomes neces- 

 sary for it to seek for its food in 

 the flowering plants, where it is 

 in a condition to be immediately 

 assimilated. The damage, there- 

 fore, to the plant is caused by the 

 hyphae, or thread-like forms of 

 the fungus penetrating the tis- 

 sues and drawing the sap and 

 nutritive fluids, and thus eventu- 

 ally starving the plant to death. 

 These hyphae are either separate 

 or in bundles; and the entire 

 mass of vegetative portion is 

 called mycelium. 



The reproduction of the fungus is by means of spores 

 which are developed on the mycelium. These spores 

 under the proper conditions of heat and moisture throw 



Fig. 57— Nematode on Carrot. 

 California Bulletin. 



