340 THALLOPHYTES 
Club Root of Cabbage.'— This is a disease of Cabbage caused 
by a parasitic Myxomycete. The Myxomycete gains entrance 
through the roots and lives upon the cells of the plant. The 
presence of the parasite causes the wart-like developments on the 
roots and stem of the Cabbage, and so injures the plant that 
no head is produced and even death often results (Figure 292). 
Within the cells of the 
Cabbage the plasmodia live 
and form spores (Figure 
293). When liberated 
through the decay of the 
Cabbage, the spores are 
carried by water, animals, 
or wind to other plants. 
The spores may lie in the 
ground and infect plants in 
succeeding years. This dis- 
ease is not only destructive 
to Cabbage but often at- 
tacks Turnips, Radishes, 
Fic. 293.— Cross section of a root Rutabagas, and Cauli- 
of Cabbage affected with Club Root, E 
showing the plasmodia () within the OWwer- The important fea- 
tissues. From Woronin. ture in controlling the 
disease consists in prevent- 
ing the spores from functioning by burning infected plants, 
treating the soil with lime or sulphur, and rotation of 
crops. 
Powdery scab of the Irish Potato.” — This disease is caused by 
one or more kinds of Myxomycetes which enter the tubers and 
roots of the Irish Potato and destroy the tissues (Fig. 294). The 
Amoeba-like plasmodia live in the cells, which, due to the presence 
1 Cabbage Club Root in Virginia. Bulletin 191, Virginia Agr. Exp. Sta., 
1911. 
Studies on Club Root. Bulletin 175, Vermont Agr. Exp. Sta., 1913. 
Studies on Clubroot of Cruciferous Plants. Bulletin 387, Cornell Uni- 
versity Agr. Exp. Sta., 1917. 
° Powdery Scab (Spongospora subterranea) of Potatoes. Bulletin 82, 
U.S. Dept. Agr., 1914. 
Powdery Scab of Potatoes. Bulletin 227, Maine Agr. Exp. Sta., 1914. 
Spongospora subterranea and Phoma tuberosa on the Irish Potato, Vol. 7, 
No. 5, pp. 213-254, Jour. Agr. Research, U. 8. Dept. Agr., 1916. 
