52 THE CUCUMBER AND TOMATO EELWORM. 



present an example of incipient atrophy of the upper valve. I 

 refer to the variety known as " Burnham Natives." An oyster 

 merchant once told me that the feeding on his "layings " tended 

 to thin out this appendage at the edge, and in proportion as this 

 thinning-out or paring-off was apparent the animal was considered 

 " true." 



^be Cucumber anb tomato lEelworm^* 



By W. Dyke. Plate VI. 



THERE is a division in the animal kingdom known to the 

 zoologist as vermes (worms). This division comprises a 

 number of diverse groups, one of which is known by the 

 name of nematoidea (Gr., nema, thread ; eidos^ form). The nema- 

 todes are, therefore, threadworms, of which more than a thousand 

 species are known. 



During the last few years many cucumber and tomato growers 

 in this country have lost a considerable number of their plants 

 annually owing to the formation of nodular enlargements (root 

 galls) upon the roots. For some time the cause of these nodular 

 formations was a mystery to growers, and not until Miss Ormerod 

 issued a report upon the subject {Report of Observations of Inju- 

 rious Insects^ etc.y 1892, pp. 127 — 137) did it become generally 

 known that the formation of galls on the roots of Tomatoes, 

 Cucumbers, and a few other plants growing under glass was the 

 work of a nematode worm called by Miiller Heterodera radicicola. 



The destructiveness of this pest is so great as to often cause 

 the grower to lose from 50 to 75 per cent, of the above-named 

 plants, and, therefore, one cannot wonder that they dread its 

 introduction into their establishments. 



Cucumber plants fall a more easy prey than Tomatoes to an 

 attack of Root eelworm. This is no doubt owing to the soft 

 nature of the tissues of the first-named plants, for I have seen in 

 several instances Tomato plants growing and fruiting fairly well in 

 houses so infested as to make it impossible to grow Cucumbers. 



* From The fournal of Horticulture. 



