118 VEGETABLE FORCING 
tomato in Fig. 38, of lettuce in Fig. 39. Serious derangement 
of the normal life functions is caused by the worms, which 
results in the development of irregular galls and the 1m- 
perfect nutrition of the plant. Evidence of infested roots 
may be indicated by the leaves becoming sickly or 
yellowish or by the stunted and dwarfed appearance of 
the entire plant. If the attack is serious, yields will be 
greatly diminished or the 
plants may die before any 
crop is harvested. The fleshy 
enlargements are watery and 
tender, and they provide 
ready entrance for fungi and 
bacteria, which may cause 
rapid decay and additional in- 
terference with the nutrition 
of the host plant. 
Nematodes migrate very 
slowly, not more than a few 
feet a year, but they may be 
introduced or distributed in 
the greenhouse by means of 
infested soil, manure and 
plants. They may be con- 
veyed about the establishment 
on the shoes of the workmen 
and on the various tools 
Fig. comes Sees foot which are used for tillage op- 
erations. 
Numerous preventive measures have been advocated. 
Chemicals of various kinds have not proved practical. 
Lime is probably of no value, for the worms will live for 
several days in a saturated solution of lime. Formalin 
has been used with slight success. Freezing, desiccation 
and inundation are valuable to some extent, but they are 
not regarded favorably by greenhouse growers. The 
