36 ROOT-KNOT AND ITS CONTROL. 



moving males in which the aUmentary canal posterior to the bulb, 

 or even including it, has entirely disintegrated, leaving the body cavity 

 filled with a granular disorganized mass except for the long testis, 

 wliich extends nearly to the esophageal bulb. The large buccal spear 

 with its complicated guiding apparatus is doubtless to enable the 

 animal to batter its way through the root tissues in its search for the 

 female, as a much smaller spear serves the female for obtaining the 

 necessary food. 



OVERWINTERING. 



The stage in wliich this nematode overwinters was made the object 

 of considerable study. In the galls on annual plants examined in 

 November it was found that in almost all cases the mature or partly 

 developed nematodes, as well as the eggs, were dead, in many cases 

 being filled with fungous threads. Larvse, however, alive and 

 actively motile, were found in abundance in and around the galls. 

 It is probable, therefore, that it is in the larval stage that the nema- 

 todes from annual plants pass the winter, probably descending into 

 the lower levels of the soil to avoid the cold. This latter point, 

 however, was not determined. In cases where the death of the top 

 of the plant had caused the death of the roots, the nematodes in the 

 roots soon died also. 



In roots of perennial plants, for example, European grape, fig, etc., 

 the writer has repeatedly found hving female nematodes in nearly 

 or quite complete development at various periods in the winter and 

 early spring, showing that in such roots the nematodes may survive 

 not only in the larval stage, as previously described, but also as 

 mature females ready to begin egg laying as soon as the weather 

 becomes favorable. 



COMPARISON WITH HETERODERA SCHACHTII. 



In view of the fact that some authors^ have questioned the correct- 

 ness of keeping separate the two species Heterodera schacJitii, the 

 sugar-beet nematode, and H. radicicola, the cause of root-knot, it 

 will be well to give briefly an account of the points of difference, 

 especially since the writer has found the former to be a serious pest 

 at several points in California and Utah, while the latter has been 

 found as a serious sugar-beet pest at some other points. In tabular 

 form the main difl'erences are easy to point out. 



1 stone and Smith, 1898; Atkinson, 1896. 

 217 



