550 DISEASES OF CULTIVATED PLANTS 



extent depending on the number of galls on the roots. This 

 injury, together with that caused by the worms drawing their 

 food from the plant, checks its growth and often kills it out- 

 right, or so weakens it that fungus diseases come in and 

 hasten its destruction.' 



The same authors state that 'the most effectual, complete, 



FIG. 167. Eelworms. i, male of Tvlenchus 

 devastatrix (after Ritzema Bos) ; 2, female of 

 Heterodera rddicicola ; 3, egg of same ; 4, section of 

 portion of a tomato root, showing two females of 

 Heterodera radicicola in section, one of which 

 contains numerous eggs. 



and practical method at the present time of exterminating 

 nematodes in greenhouses is by heating the soil by means of 

 steam. This can be accomplished without much expense, 

 providing proper attention is paid to the method of applying 

 the steam. 



