DISEASES OF GARDEK VEGETABLES. 67 



from its natural habitat till our cultivated frontier 

 reached its home, and then it spread East and North by 

 easy stages on the potato fields. 



Potato-Vine Fungus. — The potato is subject to 

 the attacks of several parasitic fuugi, two or more of 

 which attack clover and lettuce, appearing as patches of 

 white film, which, in a few weeks, spread over the entire 

 plant, extract the juice and reduce the vigor of the plant 

 so that growth of tubers ceases. There is no remedy for 

 this disease, and to prevent its spread exceedingly great 

 caution has to be observed in burning all tlie stems of 

 the infected crop. To dress the land with lime and to 

 cease to raise potatoes on the same ground for two years 

 is the best system to pursue. A second fungus growth 

 to which the potato is subject also attacks tomato and egg 

 plants, on each of which it is equally injurious. It ap- 

 pears about midsummer, and flourishes most vigorously 

 during close humid weather. It is first seen as a 

 fine white bloom, accompanied by darker spots on the 

 leaves. It is to be found mainly beneath the leaves, 

 and if the temperature continues moist it rapidly dis- 

 tributes itself over the entire plant, the darker spots, 

 increasing in number and size, indicating the joresence 

 of mycelium within the tissues soon ready to develop a 

 white material on the surface. An offensive odor is an 

 accompaniment of this disease. The fungus, under con- 

 ditions favorable to its growth, develops rapidly, some- 

 times appearing and destroying a crop in two days, but 

 always the germs of disease have been present before- 

 hand, possibly for weeks. The stems of the entire crop 

 should be burned, the land should be limed, and any 

 succeeding crop planted with seed from a district not 

 infected with the fungus, and the crop planted wide 

 apart between rows to admit of a thorough circulation 

 of air. 



Cabbage Fungus — Club-root in cabbage is a 

 name applied to the outward results which appear on 



