126 DISEASES OF THE SWEET PEA 



the host plant in which they have emerged, 

 or, as is more often the case, leave the host 

 and enter the soil. This is the only period 

 during which the worms move about to any 

 great extent in the soil, where- they either 

 remain for some length of time or immedi- 

 ately penetrate another root of the host. 

 The nematodes in most cases become com- 

 pletely buried in the root tissue, establish- 

 ing themselves in the soft cellular struc- 

 ture which is rich in food. The head of 

 the worm is provided with a boring appa- 

 ratus consisting of a sharply pointed spear, 

 located in the mouth; this structure not 

 only aids it in getting food but is also 

 valuable in helping the young worms to 

 batter through the cell walls before becom- 

 ing definitely located. The two sexes 

 during development are indistinguishable 

 up to fifteen or twenty days, both being 



