ROOT-KNOT EELWORM. 131 



characteristics of this " Eoot-knot " Eelworm that are moderately 

 easily observable, are the differences in shape of the male and female. 

 The female it should be carefully borne in mind is pear-shaped, or 

 gourd-shaped, that is, short, small at the neck, and much swelled 

 towards the base ; the base itself being either flat below, or with a 

 central depression. The males and young larvae are thread-like (or, 

 speaking more technically, Tylenchus-like) in general shape. These 

 points are very important practically. For want of due observation of 

 these characteristics, the attacks are apt to be wrongly identified, and 

 consequently serious mistakes to arise in treatment. 



Appearance of the (jailed ruuts. — The roots sent me were excellent 

 examples of extent of infestation. These specimens were from good 

 sized plants of Tomato, as the stems averaged quite an inch and a half 

 or more in circumference a little above ground level, with a good mass 

 of roots, averaging when held up as sent free from earth, about four or 

 five to six inches in length, with some longer still, and about five 

 inches in breadth. A great number of the root fibres were scattered 

 more or less thickly throughout their whole length with the root-knot 

 galls, even to the extremity, at a distance of six or eight inches from 

 the collar of the plant. 



Taking a mass of roots on one Tomato plant for special examination 

 as a specimen of amount of gall presence, I found about twenty of the 

 main roots were galled. These main roots as they branched and 

 branched again, and even on the small side fibres, were infested with 

 multitudes of irregularly shaped gall growths. Size as well as shape 

 was quite irregular. Sometimes the "knots" were mere roundish 

 fleshy lumps, about a quarter of an inch in diameter, but for the most 

 part they ran wider, sometimes to half an inch or more in diameter, 

 and very often ran to much greater length (see Plate), consequent 

 on the galls having joined, and thus forming a confluent mass along 

 the root fibre. These formed diseased swollen growths of from one 

 inch to two or three and a half inches along the root fibres, but rarely 

 averaged more than half an inch, or a little more, in diameter. The 

 form was so wholly irregular that it can hardly be described, but is 

 conveyed in the photograph. 



When I first received the galled roots (sent me on the 19th of 

 December), which had then been lying on a rubbish heap for about a 

 month, the galls appeared to be firm and healthy, but soon many of 

 them altered, in fact, fell to pieces, the bark peeling off', sometimes, 

 according to circumstance, by drying, sometimes by wet decay, leaving 

 (as noted at p. 132) merely the remains of the cells of which the gall 

 had been composed, the harder parts of the tissue of the cells forming 

 a little rough mass, a sort of miniature "rose comb-like " lump on the 

 root from which the outer coat had peeled away. 



K 2 



