sept. x6, x 9 i8 Tissue Invasion by Plasmodiophora brassicae 
571 
(14) The mass of parasitic protoplasm in a given volume of diseased 
tissue is remarkably constant in different clubs and in the clubs of 
different plants. 
(15) The average volume relation between host and parasite in the 
tissues studied is approximately given by the ratio 28 to 72. This is a 
numerical expression of the balance that exists between host and parasite. 
A unit volume of diseased tissue always yields approximately, the same 
quantity of spores. 
(16) It is suggested that noninfected cells in diseased tissues may be 
immune. 
(17) The wilting of diseased plants is in part due to hypoplasia of cell 
differentiation in the xylem portions of bundles and to the splitting up 
of the woody cylinder through the infection and growth of the medullary 
rays. 
(18) The method by which Plasmodiophora brassicae infects host tissues 
differs markedly from that of Spongospora subterranea. 
(19) If we judge by the kind of galls produced and by the position of 
diseased tissues it would seem that the method of infection for Soro- 
sphaera veronica , Sorodiscus callitrichis , and Tetramyxa palustre may be 
similar to that found for P. brassicae . 
LITERATURE CITED 
(1) Atkinson, G. F. 
1889. nematode root-galls. Ala. Exp. Sta. Bui. 9, 54 p., 6 pi. List of works 
consulted, p. 50-52. 
(2) Chupp, Charles. 
1917. studies on clubroot op cruciferous plants. N. Y. Cornell Agr. Exp. 
Sta. Bui. 387, p. 419-452, fig. 95-100. Bibliography, p. 451-452. 
(3) Eycleshymer, A. C. 
1891. club-root in THE united states. In Jour. Mycol., v. 7, no. 2, p. 79-88, 
fig. 7-8, pi. 15-16. 
(4) Favorski, V. I. 
1910. NEW data on the cytology with life history of plasmodiophora 
brassicae wor. In Mem. Kiev. Soc. Nat. Sci., v. 20, no. 4, p. 149-183, 
pi. 5-6 (partly col.). In Russian with resum£ in French. 
(5) FerdinandsEn, C., and Winge, 0 . 
1914. ostenfeldiella, A new genus OF plasmodiophoraceaE. In Ann. Bot., 
V. 28, no. 112, p. 643-649* 4 fig** pl* 45 * 
(6) Goebel, K. 
1884. tetramyxa parasitica. In Flora, Jahrg. 67, no. 28, p. 517-521. 
(7) Karelschtikoff, S., and Rosanoff, S. 
1870. note sur les tubercules du callitriche autumnalis. In Mem. Soc. 
Imp. Sci. Nat. Cherbourg, t. 15 (s. 2, t. 5), p. 124-136, pl. 5. 
(8) KOster, Ernest. 
1911. DIE GALLEN DER PFLANZEN. 437 P*» x 5 8 fig* Liepzig. 
(9) Kunkel, L. O. 
1915. A contribution to the ufe history of spongospora subterranea. In 
Jour. Agr. Research, v. 4* no* 3* P* 265-278, pl. 39-4 3* Literature cited, 
p. 278. 
70394 p —18 - 4 
