8 BULLETIN 75g, U. S. DEPARTMENT OF AGRICULTURE. 
By careful comparison in this manner it has been found possible to 
distinguish between the two species on the basis of spore measure- 
ment alone. 
In addition to the difference in size, there is a difference in shape 
that is discoverable by the examination of many spores — a difference 
that does not significantly appear in measurement. Some of the 
spores of Pseudopeziza trifolii are slightly flattened on one side. 
When the flattened side is seen in profile the spore has a somewhat 
pointed appearance. The occurrence of occasional pointed spores 
(fig. 1) is a distinguishing feature of this species. 
Spores from dried specimens have not been found satisfactory for 
comparative measurement. Unless the collection is made just before 
the apothecium is completely mature, nearly all of the spores are un- 
avoidably discharged during drying. The few remaining are likely 
to be found much shrunken. 
MORPHOLOGICAL CHARACTERS IN CULTURE. 
MYCELIUM. 
In culture these fungi preserve the same general characteristics 
that they show on the host plant. The mycelium radiating from the 
germinating spore or group of spores soon produces a stroma at the 
center. Thereafter this stroma is surrounded with a narrow fringe 
of hyphse, which never advance far beyond the stroma. When the 
fungi are grown from spores on the same nutrient substratum, differ- 
ences in the character of the mycelium can be noted. That from 
Pseudopeziza •medicaginis branches earlier than that of P. trifolii; 
most of its branches come off at an acute angle, while those of P. 
trifolii come off somewhat regularly at a right angle, or occasionally 
at an obtuse angle. 
COXIDirMLIKE STRUCTURES. 
Although no conidia have been found in nature, conidiumlike struc- 
tures occur regularly in culture and are a feature by which cultures 
of the two species can be most easily distinguished. They arise from 
the ends of branches or from the distal ends of somewhat swollen 
cells. They measure 5 to 8 by 3 to 5 microns. They occur most abun- 
dantly when the ascospores are germinated on clear agar to which 
no nutrient has been added, appearing in about three days in the 
case of Pseudopeziza medicaginis and somewhat later on mycelium 
of P. trifolii. On mycelium of the first fungus they are produced in 
great abundance before the end of the first week, though the mycelium 
from different spores or groups of spores produces them in varying 
amount. (Fig. 3.) The mycelium may grow but little, becoming 
thickly covered with the conidia. or it may grow more freely with 
but a few conidia at the ends of short branches. Earelv are thev 
