8 EOOT-KNOT AND ITS CONTROL. 



decreasing diameter toward the tip, they show irregular enlargements 

 which involve the whole root if it be small or sometimes only one side 

 of a large root. (Pis. II and III.) These are not superficial swell- 

 ings only slightly attached to the root, as in the case of the bacterial 

 tubercles of leguminous plants, but are integral parts of the root itself. 

 On small roots these swellings may vary from only slightly greater 

 than the thickness of the root to twice as thick, and spherical to spindle 

 shaped; on larger roots they are usually lateral, or in bad cases may 

 involve all sides, making a gall many times the normal diameter of 

 the root and covered with furrows and seams until the root loses all 

 semblance of its normal appearance. Such compound knots may 

 reach a diameter of 3 or, rarely, even more centimeters and a length 

 many times as great. 



HISTORY OY ROOT-KNOT.' 



Root-knot has been known for many years both in the United 

 States and abroad. It was apparently first mentioned in print by the 

 famous mycologist Rev. M. J. Berkeley ,2 who described and figured 

 roots of plants affected by this disease and recognized the animal na- 

 ture of the organism causing it. The galls were observed by Greef on 

 grass roots in 1864, but it was not until 1872 that the parasite received 

 a name,^ Anguillula radicicola Greef, after it had been observed sev- 

 eral times on a number of different plants. In 1879 Cornu described 

 this species, observed by him on sainfoin in 1874, as A. marioni. In 

 1882 and 1885 the well-known plant pathologist. Prof. A. B. Frank, 

 described it as a serious enemy of a number of cultivated plants in 

 Germany. In 1883 and 1884 C. Miiller made a careful study of the 

 organism causing the disease and placed it in the genus Heterodera 

 under the name of Heterodera radicicola (Greef) Midler. He showed 

 it to be a close relative of the destructive sugar-beet nematode Hete- 

 rodera scJiachtii Schmidt, which has caused so much injury to the beet- 

 sugar industry in Europe and which the writer found in 1907 in 

 scattered localities in the United States. Treub in 1885 described as 

 a parasite of sugar cane in Java what he considered to be a new 

 species, naming it Heterodera javanica. This is considered now by 

 most authors to be a synonym of H. radicicola. 



In the United States the root-knot early attracted the attention of 

 greenhouse men as a serious pest of roses, violets, and other plants. 

 J. N. May states ^ that he saw the disease, which he calls "club-root," 

 on violets in 1876. We fmd the florists' papers full of references to 



1 The full titles of all papers mentioned in this bulletin will be found in the " Bibliography," pp. 76-81. 

 The a,b,c following a dale, if given, refer to the first, second, and third papers published if more than one 

 paper in that year is referred to. 



■i Berkeley, 1855. 



3 Greef, 18G4 and 1872. 



1 May, 1888. 

 217 



