128 MASSACHUSETTS HORTICULTURAL SOCIETY. 



from higher to lower fields by floods ; some have been carried by 

 the plow or other tools, or on the feet of animals. Occasionally man 

 himself digs them up and transports them into hotbeds, green- 

 houses, and fields. One year all of our potting soil at the Depart- 

 ment was so badly infested with the damp-off fungus that plants 

 could be gotten past the seedling stage only with great difficulty. 

 Frequently these fungi creep through the earth for considerable 

 distances, destroying nearly everything they meet or only certain 

 species of plants. Others distort or corrode underground parts 

 without destroying the plant. Onion smut, potato scab, the club- 

 root of cruciferous plants, the fairy-ring fungus, Rolf's sclerotium 

 disease, the cotton root rot ; the De'm,atoj)liora necatrix, destructive 

 to the roots of grape vines, figs, and many other plants ; the 

 Polyporus cmnosus ; Trametes radiciperda, especially destructive 

 to the roots of coniferous trees; and the root fungus of New 

 Zealand, which is said to destroy every sort of plant in its way, 

 are examples of these soil parasites. I shall mention particularly 

 only one type of these troubles, viz. : 



The Fusarium Diseases of the United States. — It has fallen 

 to my lot to study some of these parasites quite carefully, and I 

 now know eight important cultivated plants subject to them, viz., 

 cotton, cow-pea, watermelon, cabbage, potato, tomato, sweet 

 potato, and pineapple. Whether we have liere to deal witli eight 

 parasites or with only one widely distributed polymorphic organ- 

 ism remains to be determined. I am inclined to think, however, 

 from my own numerous experiments, covering a series of years 

 and not yet completed, that we have to do with closely related 

 but distinct forms. All of these host plants are seriously in- 

 jured and some of them over wide areas. In all of them the 

 trouble is due to a sort of embolism or parasitic clogging of the 

 water ducts of the plant. I have already alluded to the water- 

 melon wilt when speaking of parasites disseminated in barnyard 

 manure, and will here devote most of my remarks to that disease. 

 It occurs from the Carolinas to Texas, and has practically put an 

 end to profitable melon culture in parts of South Carolina, 

 Georgia, Florida, and Texas, The plants are attacked in all 

 stages from seedlings to mature vines in fruit. The first sign is 

 a sudden wilting of the whole or a part of the vine without 

 apparent cause. The fungus enters the plant from the soil and 

 almost always destroys it. I have seen large fields entirely 



