ELISHA MITCHELL SCIENTIFIC SOCIETY. 105 



tunity should occur for its introductiou into our States even so 

 far north as New York and Ohio tliat from its habit it might 

 easily pass the winter in sufficient numbers to become a terrible 

 pest. On long rooted plants like the parsnip I have found them 

 in great numbers fifteen inches below the surface of the ground. 

 On tomato roots, which were placed in the soil very deep to get 

 them if possible out of the way of the attacks of the worms, I 

 have found them so low as eighteen inches below the surface. 

 This depth would protect them from the frost in the very severe 

 winters of some of our Northern States. 



There is to some extent a natural barrier to the spread of the 

 root-gall nematode from the Southern to the Northern States, 

 which is explained by the fact that very few, if any, perennials 

 grown in the South are transported North for cultivation. How- 

 ever, the subject is of sufficient importance to the Northern 

 States to justify an inquiry into the possibility of its being suc- 

 cessfnlly carried through the winter under the conditions I have 

 stated. 



VI. 



STRUCTURAL CHARACTERISTICS OF THE DISEASED ROOTS. 



Nomenclature. — The abnormal growths on the roots caused 

 by Hcterodera radicwola have long been termed popularly, in 

 this country, " root- knot." In Scotland they are known as 

 *" root-ill," "thick-root," "tulip-root," "segging"; while in 

 Germany they have long been known under the name " Wur- 

 zelgallen." The tubercular swellings on the roots of leguminous 

 plants (see comparison of root-galls with the tubercles of the 

 Leguminosece at close of this section) have long been known and 

 published in Germany as " Wurzelknollchen " (root-knot). In 

 order to avoid a confusion of the tubercle with the abnormal 

 growths dealt with here I shall use the term nematode root-gall, 

 or root-gall. There is a tendency with some writers to use the 

 term "gall" only for those abnormal growths which have their 



*Smith, W. G. Disease of Oafs — Heterodera radicicola, Muller, Gardeners' Chron., 

 New Ser., Vol. XXVI, p. 172, 1886. Abstract in Bot. Ceutralblatt, Bd. XXXI, p. 247, 1887. 



