HETERODERA RADICICOLA. 417 



Botany. My hearty thanks are also due to the Research Grant 

 Board, for their grant-in-aid, which facilitated the collecting of 

 material and conducting the investigation. 



Summary. 



(/) The structure and development of Heteroilera radicicola is 

 described and figured for the first time in South Africa. The 

 occurrence of only two ecdyses in the course of development is 

 established : one taking place when the larva is living free in the 

 soil, and the second during the differentiation of the two sexes 

 within the root of the host. For the most part the material used 

 in these investigations was obtained from parasitised potatoes, 

 and this organism was seen to differ substantially in some characters 

 from //. radicicola found in tomato plants and others. These 

 differences are detailed, but it is thought that they may be varia- 

 tions due to environment and may not be of true specific value. 



(ii) The species Heterodera schachtii and //. radicicola are 

 discussed and their differences tabulated, and they are compared 

 with the parasite found in potato tubers. 



(Hi) The pathogenicity of the parasite and the mode of 

 infection is discussed. Some susceptible host plants found in South 

 Africa are listed. The geographical distribution of the parasite 

 is set forth. 



(iv) The methods of controlling the pest are briefly reviewed 

 and an attempt is made to estimate their relative values in South 

 Africa. 



References. 



All the references to literature contained below have been 

 seen by the author. For a more extensive bibliography the work 

 of Bessey (1911) should be consulted. 



Atkinson, G. F. : "A preliminary report upon the life history 

 and metamorphoses of a root gall nematode, Heterodera 

 radicicola (Greef Muller) and the injuries caused by it upon 

 the roots of various plants." Agric. Expt. Stn., Alabama 

 Polytechnic Inst., Auburn, Ala. Vol. I., No. 1, December, 

 1889. Bull, of Agric. Expt. Stn. n.s., No. 9, 1889; 54 pp., 

 6 pi. 



Bessey, Ernest A.: "Root Knot and its Control." Bull. 217, 

 Bureau of Plant Industries, U.S. Dept. Agric, 1911. 81 pp., 

 3 pi. 



Cobb, N. A.: "Root Gall." Agric. Gaz. of New South Wales, 

 Vol. 13. Sydney, 1901. 



" Fungus Maladies of the Sugar Cane." Bull. 6 of the 

 Expt. Stn. of the Hawaiian Sugar Planters' Assn. (1909), 

 pp. 51-62. 



Lounsbury, C. P.: "Gall Worms in tlie Roots of Plants. An 

 important potato pest." Circular 25. Cape of Good Hope 

 Agric. Dept., 1904. 



