228 ROOT-KNOT EELWORM. 



causing so much loss where it does establish itself, that a short 

 description of the nature of the infestation may be of use. 



Ajypearance of the galled roots. — The galls on the various 

 kinds of plant roots on which I have seen them, that is, on 

 roots of Tomato, Cucumber, and Lettuce, sent me for examina- 

 tion, were small knobs, or irregularly shaped lumps, varying 

 in size from an eighth of an inch or less in diameter to (in the 

 case of the Tomato) fleshy lumps a quarter of an inch to half an 

 inch or more in width, and much more in length ; even to as 

 much as one, two, or over three inches of irregular swollen gall 

 growth along the root fibres where the galls were confluent. 



Taking a mass of roots on one of a number of good-sized 

 Tomato plants, averaging an inch and a half or more in 

 circumference a little above ground level, for special examina- 

 tion 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 dia- 

 meter, and ver3' often ran to much greater length than this, 

 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. 



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 oft", sometimes, according to circumstance, by drying, 

 sometimes by wet deca_y, leaving 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 or lumj) 

 on the root from which the outer coat had peeled away. 



The enormous amount of Eelworm presence in the galls 

 was enough to spread infestation in the earth, and to all 

 plants near which were cajiable of receiving it. 



The following notes of the life-history of this root pest are 

 abridged from the excellently minute observations by Prof. 

 Geo. F. Atkinson, referred to below.* 



* ' A Preliminary Eeport upon the Life-history and Metamorphoses of a 

 Root-gall Nematode, Heterodera radicicola (Greef.), MiilL, and the Injuries 

 caused by it upon the roots of various plants,' by Geo. F. Atkinson. Science 

 Contributions from the Agricultural Experiment Station, Alabama, U.S.A., 

 December, 18S'J. 



