H74 
Journal of Agricultural Research 
Vol. V, No. as 
Rhizoctonia sp. isolated from alfalfa proved fatal to cotton seedlings. 
Two weeks after inoculation all of the young plants were dead. On the 
contrary, a species of Rhizoctonia from potato produced no noticeable 
injury to cotton seedlings. This difference in the action of the two 
strains of Rhizoctonia is very evident from Plate LXXXIII, figure 6, and 
the data in Table XV. A species of Rhizoctonia from alfalfa produced 
nearly the same effect on soybeans as on cotton, while the germination 
of Corn was not affected. 
A study of the optimum conditions for the growth of culture i and 
Rhizoctonia sp. from alfalfa showed that about 25 0 to 30° C. is the most 
favorable temperature for both of these fungi. The results of a previous 
study indicate that about 25 0 C. is the optimum temperature for the 
growth of the harmful factor. Prom the data as a whole, it seems very 
conclusive that the fungus of culture 1 and probably other fungi are the 
causative agents in the destruction of germinating seeds. 
DESCRIPTION OF THE INJURY 
Examination of the diseased seeds shows that the injurious factor 
probably does not attack seeds until after germination. Apparently the 
fungus attacks the primary root soon after germination. This occurs 
when the primary root is from to 1 cm. long. The hyphae pierce the 
walls of the host, entirely envelop the root, and often penetrate deep 
within the tissue. In the affected region the tissue loses its form, turns 
brown in color, and soon rots. Under the microscope these diseased 
seedling roots are surrounded by a dense mantle of hyphae, which are 
often brown-colored. 
RELATION OF GREEN MANURE TO INJURY OF OIL SEEDS 
Although the evidence at hand does not warrant a definite conclusion, 
the author suggests the following as a possible explanation for the injury: 
The green tissue furnishes an excellent medium for the development of 
fungi. This is especially true in the first stages of decomposition. After 
one or two weeks in the soil the green manure undergoes certain changes 
which render it unsuited to the growth of the injurious,fungi. 
Just why oily seeds should be so sensitive to fungi is not known. It is 
possible that the oil partly changes to fatty acids in the process of germi¬ 
nation (9, 10). According to Schmidt (19, p. 300-303), oil and fatty 
acids favor the growth of certain fungi. The fungus may produce a 
fat-splitting enzym—for example, lipase. This offers a possible expla¬ 
nation for the selective action of the injurious fungi for oil seeds. 
