10 
C. Experiment Station 
]STo observable differences were noted in tlie size and manner of pro¬ 
duction of tbe apparently functionless microconidia. These structures 
are small, spherical bodies, 2 to 4 mikra in diameter, which are ab- 
stricted in acropetal succession from flask-shaped cells. These cells may 
appear as lateral or terminal branches from the vegetative hyphae, Plate 
1, Fig. 2, or from the germ tubes produced in the germination of the 
ascospores. Microconidia may form in conspicuous, grayish, mealy 
patches on the surface of the mycelium in culture. They have not been 
observed to germinate except by the formation of a hypha 2 or 3 mikra 
long, nor has it been possible to bring about infections with them. This 
accords with the results by others, among whom are Coleman (4). 
During April, 1916, twenty crimson clover plants were sprayed with a 
suspension of microconidia from S. trifoliorum, were then covered to 
conserve moisture but no sign of infection was subsequently noted. 
The macroscopic characters of the apothecia cannot be employed in 
differentiating the two forms. The stipe and disc are yellowish brown 
in color. The stipes are variable in length, depending upon the depth 
below the surface of the soil to which the sclerotia are buried. In ex¬ 
treme cases their length varies from 3 to 30 mm. and their thickness 
from 1 to 2 mm. The discs are at first deep cup-shaped, but expand to 
a flat disc, 3 to 10 m.m. in diameter, the margin of which may become 
reflexed and fissured, Plate 1, Fig. 4. Apothecia of both species have 
been secured by the writers by burying selerotia from 2 to 9 months in 
moist sand in flower pots. Sclerotia of S. trifoliorum which had been 
matured in culture in July, 1910, were planted during September and 
they had developed fruiting discs by December, Plate 3, Fig. 2. Com¬ 
parative measurements of asci and ascospores from these apothecia, as 
indicated in text, Plate 1, Fig. 3, show that the asci and ascospores of 
S. trifoliorum are very manifestly larger than those of S. libertiana 
which facts accord with observations of other investigators. These data 
are assembled in the following tabulation: 
SCLEROTINIA TRIFOLIORUM 
SCLEROTINIA LlBERTIANA 
Author 
Size of Asci 
Size of 
Ascospores 
Author 
Size of Asci 
Size of 
Ascospores 
Rehm . 
160x10* 
15-17x8-10* 
Saccardo 
130-135X 
9-13x4-6.6* 
Eriksson . . . . 
180x12* 
14-18x8* 
8-10* 
Kuhn . 
160-180x14* 
16-20x8-10* 
Stevens & 
82-2(?) 
8.7-11.6x5.8* 
Present 
140-160 
12-14x8* 
Hall . . . . 
writers. . . 
8-11* 
Present 
95-120X 
7-9x6* 
writers. . . 
8-9* 
*Mikra. 
