29 



that nematodes propagate by eggs and any method which fails to 

 destroy these is of little account. Could we succeed in ridding 

 badly infested soil of adult nematodes it would only be a matter of 

 one or two weeks before the soil W'ould be swarming again with 

 nematodes ready to attack their proper host. Our experiments both 

 in the greenhouse and laboratory have repeatedly demonstrated this, 

 and this fact is interesting as showing how badly infested soil may 

 become with nematode eggs. It is verj^ clear that any remedy which 

 is to be applied to the soil for the purpose of completely ridding it 

 of nematodes must be one which will not only kill all of the worms 

 but their eggs as well. It is, in fact, the eggs of the nematode 

 which constitute the most difficult factor in their control as they are 

 surrounded by a more or less impenetrable membrane and we have 

 not as yet discovered any solution capable of destroying them in the 

 soil which can be employed cheaply and effectively without injury to 

 the crop. 



Plants which are Subject to Nematodes. 



The plants which are subject to nematode ravages are quite 

 numerous and they represent a great many different families. Prof. 

 Kiihn' in i88t gave a list of i8o European plants belonging to 35 

 different families w'hich nematodes attack and this list has undoubt- 

 edly been enlarged since that time. The most susceptible families 

 according to Kiihn's list are the Gramineae (Grasses) in which there 

 are recorded 46 species of plants subject to nematodes, while the 

 Leguminosae (Clovers, etc.) is represented by 33 species, the 

 Compositae (Aster, etc.) by 16 species and the Cruciferae (Mustards, 

 etc.) by 14 species. Neal in his work entitled "The Root-Knot 

 Disease of Plants " has enumerated over 60 species of plants in 

 Florida susceptible to the attacks of nematodes, and Atkinson (1. c.) 

 has listed 36 different plants observed by him in Alabama. 



In our Northern States the number of plants attacked by nema- 

 todes is very much smaller and is almost entirely confined to green- 

 house species. In the North the greenhouse cucumber, tomato, 

 violet, rose, and cyclamen constitute the most important host plants, 

 although they are not infrequently found causing considerable dam- 



I. Die Ergebnisse d. Versuche z. Erniittelung d. Ursache d. Riibenmudigkeit u. 

 Erforschung d. Natur d. Nematoden. p. 120, iSSi. 



