608 
Journal o f Agricultural Research 
Vol. XXXI, No. 7 
August have germinated in January, and sclerotia planted in April 
have germinated and produced apothecia in April. The shortest time 
between planting and germination was 18 days, while the longest was 
141 days. From this it seems safe to assume that the time of apo- 
thecial production depends entirely upon ecological conditions such as 
moisture, temperature, and light. Variations in the length of time 
between date of planting and date of germination, as shown in Table 
III, must be attributed to these ecological factors rather than to 
differences between strains of 8. libertiana. 
Small sclerotia are especially susceptible to decay when the pots 
are kept too moist, and for this reason it is usually much more difficult 
to obtain apothecia of the small scl 4 erotial forms than from those of the 
S. libertiana type. Various investigators have found that the 
sclerotia of S . libertiana will remain alive in dry state for several 
years, but it is usually agreed that in nature most of them decay 
during the first year. In this connection it is interesting to note, 
however, that Pollock (28) has given evidence to show that the 
sclerotia of Sclerotinia cinerea (Bon.) Schrot. may remain alive for 
10 years in fallen mummified fruits. 
As noted by Stevens and Hall (29), the light factor has been found 
to be especially prominent in stimulating the full development and 
expansion of the disk-shaped apothecium. Small, hornlike out¬ 
growths are often found growing from sclerotia in old test-tube 
cultures which have been stored in the dark, but the writer has never 
known of one to expand into a normal apothecium. These aborted 
apothecia are quite common in sand-pot cultures that have been held 
in weak light. In some experimental pots used by the writer, more 
than 100 apothecial stalks have started out normally and then failed 
to expand presumably because of unfavorable light conditions. 
When these pots were placed in good light, the apothecia which started 
out subsequently developed in a normal manner. Abnormal and 
freakish apothecia are often formed when unfavorable growing con¬ 
ditions alternate with conditions favorable to growth. This stopping 
and resuming of development often leads to such freaks of apothecia 
as shown in Plate 2, B. 
SINGLE ASCOSPORE ISOLATIONS 
When apothecia are allowed to mature and fully expand under a 
bell jar, it is comparatively easy to obtain single spore cultures. 
A smokelike cloud of ascospores is discharged almost immediately 
upon a change of humidity brought about by lifting the bell jar. 
This cloud of ascospores is visible even when only one apothecium 
discharges, owing to the fact that even a moderate-sized apothecial 
cup may contain an enormous number of spores. Stevens and Hall 
(29) estimated that one cup may produce 31,000,000 spores. If a 
large number of apothecia are ripened at the same time and held 
under cover so that their discharge can be controlled, it has been 
found possible to photograph this cloud of spores as it rises into the 
air. 
Dickson and Fisher (12) devised a method by which an excellent 
photograph of the spore-cloud emanating from apothecia of S. 
libertiana was obtained. By holding a Petri dish containing a thin 
layer of nutrient agar inverted over a discharging apothecium, a 
large number of the spores are shot against agar surface. The 
