ROOT KNOT IN THE TOMATO. 



the cuttino; back of the plants never seems to invig-orate them. 

 Tlie worm itself is thireadlike, white, slig'htlv flattened, and varies 

 in length from about 300 to .SOO/i, and shows fine cnticular rings. 

 The oral end is slightly tapering and rounded, but the tail end 

 tapers to a sharp hyaline point. The American species is g^iven 

 as being over i mm. in length and the tail end rounded. T 

 have found no signs of moulting as described for the American 

 species. In this species there is therefore no stage that can be 

 considered as a larval stage. There are no sj^ines on the tail — 

 which is perfectly smooth — so that identification is rather difificult. 

 and there is no definite bend in the tail to distinguish the male. 

 There is apparently no difference between the male and female 

 in the Aoung stage, but a difference soon appears, probably after 

 fertilisation has taken place. The female is then seen to be wider, 

 with more granular contents, a more blunt tail, and shows the 

 genital pore in the middle. It then takes up a permanent position 

 in the root, and the gall swellings made of i)arenchyma are pro- 

 duced by the plant. It slowly changes its shai)e, becoming wider 

 and wider, and finally flask-shaped, the tissue of the gall being 

 dissolved or absor1)ed to make room for it. In this way the gall 

 has scattered through it small spherical spaces made of the female 

 bodies. These spaces can be seen with the naked eye as small 

 whitish circular patches of about -J mm. in iliameter when a gall 

 is cut across. There is no definite lining to the spaces, but a more 

 or less dense rind of parenchyma is found around each. Occa- 

 sionally a clear lining can be seen around a young space, which i> 

 probably the wall of the female body, but this soon disappears. 



The neck of the worm also gradually disappears and eggs begin' 

 to make their appearance in the rounded portion until each space 



