Mar. so, 1916 Relation of Green Manures to Failure of Seedlings 
ii73 
According to many investigators, fungi may injure seed germination 
(1, p. 30-39; 7, 12, 15). For example, Muth (15) found Aspergillus niger 
harmful to the germination of various seeds, while Atkinson (i, p. 30-39) 
and Bolley (5, p. 25-27) report a destruction of cotton and flax seed¬ 
lings by species of Rhizoctonia and Fusarium. 
Since it is established that certain soil fungi are injurious to very 
young seedlings, the question arises as to the occurrence and growth of 
parasitic fungi in green-manured soil. An experimental study of the 
occurrence of fungi in green-manured soil was made. Microscopical 
examinations of the diseased seeds showed the presence of many fungi 
on the primary root tip. Although no systematic study was made, 
some of the forms showed certain characteristics of the genus Rhizoc¬ 
tonia and others of the genus Fusarium. From portions of the diseased 
tissue plates were poured. In this way several species of fungi were 
isolated. These are described under laboratory numbers. All attempts 
to secure a pure culture of any species of Rhizoctonia failed. The vari¬ 
ous fungi were used to inoculate large tubes and jars of sterilized green- 
manured soil. The inoculated soil was planted to bacteria-free cotton¬ 
seed and soybeans. In the soil cultures no injury to germination was 
noted, except with culture 1. Here from 75 to 100 per cent of the seed¬ 
lings were killed. Repeated tests with this unknown culture gave simi¬ 
lar results. No injury to corn and wheat was noted from inoculations of 
culture 1, while soybeans and cotton were quickly destroyed. 
Since the diseased root tips showed the presence of a Rhizoctonia-like 
fungus, it was arranged to study the effect of certain species of Rhizoc¬ 
tonia isolated from other sources. Two strains were employed—one 
isolated from potatoes, the other from alfalfa. The potato culture was 
secured from the Department of Plant Pathology of the Wisconsin 
Experiment Station; the alfalfa culture was supplied by Mr. Fred Jones, 
of the University of Wisconsin. Table XV gives the results of this test. 
Table XV .—Effect of Rhizoctonia spp. on the germination of cottonseed 
No. 
Treatment and inoculum. 
Germination. 
Relative. 
1 -week. 
3 weeks. 
3 weeks. 
Per cent. 
Percent . 
Per cent. 
Percent. 
1 
None, sterilized. Uninoculated. 
75 
80 
80 
IOO 
2 
1 per cent clover sterilized. Uninocu¬ 
lated. 
80 
8S 
85 
105 
3 
None, sterilized. Inoculated with Rhizoc¬ 
tonia sp. from alfalfa. 
60 
70 
70 
86 
4 
1 per cent clover sterilized. Inoculated 
with Rhir-ar.tpnid Sp- from alfalfa. 
5 
None, sterilized. Inoculated with Rhizoc¬ 
tonia sp. from potato. 
80 
80 
80 
IOO 
6 
1 per cent clover sterilized. Inoculated 
with Rhizoctonia sp. from potato. 
• 85 
8S 
85 
105 
