Oct. i, 1925 Sclerotinia Species Causing Decay of Vegetables 
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microconidia on the vegetative mycelium, it seemed of first import¬ 
ance to determine whether these microconidia were capable of 
germination. In this study the methods employed were, in general, 
very similar to those used by Duggar (IS) in his studies on'the 
germination of certain fungous spores. The extremely small size 
of the microconidia and their lack of color make working with them 
very difficult. In order to use the high power of the microscope, it 
was necessary to make practically all study with hanging-drop 
cultures. While miscellaneous experiments were conducted with 
numerous cultures from time to time in attempts to get the micro¬ 
conidia to germinate, the greater part of the work was centered about 
50 strains of Sclerotinia, including S. libertiana, S . intermedia , S. 
ricini , and S. trifoliorum. These cultures represented a host range 
of 30 plants which are commonly affected bv Sclerotinia and which 
were obtained from widely separated parts of the United States. 
The more important nutrient solutions and materials used in the 
germination studies, testing out the ability of the microconidia of 
Sclerotinia species to germinate, were: 
Distilled water, water distilled in glass, tap water, sterile tap water, fresh 
rain water, sterile rain water, liquid exudate from newly forming sclerotia, 
freshly cut slices of carrot roots, leaves of head lettuce, sterile distilled water 
with bits of fresh carrot tissue, celery tissue, and lettuce tissue added separately, 
freshly expressed juice of salsify roots, carrot roots, beet roots^ turnip roots, 
rutabaga roots, lettuce leaves, celery stalks, ripe tomato fruit, lemon fruit, 
alfalfa stems, clover stems, decoctions of each of all these plants, soil decoction, 
ant decoction, beef bouillon, prune juice, sugar solutions, standard nutrient- 
salt solution, Pfeffer’s nutrient solution, liquid gelatin, hard gelatin, potato agar, 
potato-dextrose agar, prune agar, and oat-meal agar. 
In practically all experiments, hanging drops of the nutrient solu¬ 
tion containing microconidia were made in Van Tieghem cells, and 
held at room temperature in diffused light. In most instances 
duplicates were placed in an incubator at a temperature of approxi¬ 
mately 8° C. In many cases microconidia were separated from a 
suspension of mycelium and spores by filtering through filter paper. 
The filtrate containing the microconidia was then used to flood over 
agar and gelatin plates and to spray on host plants and on parts 
oi their organs. As a rule, cultures were held for one week and 
examined daily for germination. 
In the first hanging-drop cultures, tap water, distilled water, and 
rain water were used as a medium in which to test out the germina¬ 
tion of microconidia. But such poor results were obtained (pi. 4, 
A, B, G, and D) that in order to find out whether substances present 
in the tap water or traces of copper in the distilled water were acting 
as toxic agents these were distilled in glass and used as media in 
further studies. These results, however, were no more favorable 
than the others. Short germ tubes started in several cultures within 
12 to 24 hours, but the growth then stopped and no changes in 
temperature or light conditions were found that would induce further 
development (pi. 4, E and F). 
From the results obtained with the water-culture experiments it 
appeared that microconidia belong to that class of spores which 
require a nutrient or some stimulating agent in order to germinate 
well. In view of the fact that Brown (1 0) found a decided stimulat¬ 
ing effect produced by the volatile substances arising from bruised host 
