170 Eelworms [CH. 
The culprit in this case is known as Tylenchus 
scandens. 
In this disease the grains of wheat are affected. 
They become rounded or irregular in shape and are of 
a dark or purplish colour. If a portion of the inside 
of a diseased grain is examined in a drop of water it is 
found that the thread-like bodies composing the mass 
begin to move about, and by their structure show them- 
selves to be parasitic eelworms. The eelworms are 
said to crawl up on the outside of young plants and 
enter the developing flowers. 
Remedial Measures. 
The grains containing the eelworms are very light 
and float to the surface when wheat is steeped and are 
easily skimmed off. 
Root Knot. 
The eelworm which produces knots on the roots of 
a large number of plants is known as Heterodera radi- 
cicola. It may also be found at the base of the main 
stem which is below the ground (see Fig. 54). 
This eelworm is peculiar in that the female after 
being fertilized swells and becomes almost spherical 
(see Fig. 51 D) 
Inside the knots formed by this eelworm are small 
white balls which when examined under the microscope 
show themselves to be eelworms. The males are very like 
T'ylenchus. These eelworms flourish best on sandy soils. 
Remedial Measures. 
In fields this disease can be reduced by means of 
gas lime. In greenhouses it may be kept down by 
watering heavily or by partial sterilization. 
