THE GENUS HYSTERIUM AND SOME OF ITS ALLIES. 627 
in the shape of black specks or crusts which, under a lens, will be 
seen to be small, boat-shaped bodies with a vulveform fissure 
looking like minute grains of black wheat. When developed in 
or on wood, their structure is usually carbonaceous and brittle. 
When developed beneath the epidermis of leaves or herbaceous 
stems, the perithecium is usually thin and iii Dili ace and 
more or less connate with the surrounding struc 
The difference in fruit is also well-marked Lr obi these latter 
forms will be referred to the genus Hypoderma. 
For the identification of the species of this genus in the present 
state of our knowledge, we must rely mainly upon the size, shape, 
structure and color of the spores, and hence a few words are nec- 
essary with regard to the morphology of the spore. Spores vary 
according to age and some other circumstances in all the points 
upon which we rely. Thus the same spore at different periods may 
be colorless or very dark colored, uniseptate or multiseptate, fusi- 
form or obovate, and from .0005 to .002 of an inch in length. 
The limits of this variability are not precisely known, but the 
student may be guided somewhat by the fact that the development 
of spores and asci is not everywhere simultaneous in the same 
perithecium. When in any ascomycete we find the perithecium 
fully developed, and all the spores apparently equally mature— 
for instance, all yellow brown, triseptate and varying not greatly 
in form and size,—we are sneShes, I think, in concluding that 
these spores are mature. 
If, on the other hand, we find that some of the asci do not con- 
tain spores, but merely the mass of greenish colored protoplasm 
which by segmentation will ultimately form them, while other asci 
contain greenish spores the contents of which are divided into 
two or four parts—and in none do we find colored or oleh sep- 
tate spores — we may consider the specimen as immatur 
The peculiar greenish hue of the spore, to which I Ea alluded, 
seems to indicate that it is an immature state of a yellow or 
brown spore, while a white, perfectly colorless or hyaline spore 
may be in itself a perfect form. In the examination of specimens 
which have been for some time in an herbarium, we should expect 
to find the spores mostly mature, as in the first place it is to be 
presumed that only the more perfect specimens would be thus pre- 
served, and secondly, the perfecting and ripening of immature 
spores will go on, even in the herbarium, to some extent. 
AMER. NATURALIST, VOL. V. 40 
