132 FUNGI. 
observed for a time a whitish cloud will be seen to rise suddenly 
from the surface of the disc, which is repeated again and again 
whenever the specimen is moved. This cloud consists of 
sporidia ejected simultaneously from several asci. Sometimes 
the ejected sporidia lie like frost on the surface of the disc. 
Theories have been devised to account for this sudden extrusion 
of the sporidia, in Ascobolus, and a few species of Peziza, 
of the asci also, the most feasible one being the successive 
growth of the asci; contraction of the cup may also assist, as 
well as some other less potent causes. It may be remarked 
here that the sporidia in Peziza and Helotium are mostly colour- 
less, whilst in Ascobolus they pass through pink to violet, or 
dark brown, and the epispore, which is of a waxy nature, be- 
comes fissured in a more or less reticulated manner. 
The sporidia in Hysterium proper are usually coloured, often 
‘multiseptate, sometimes fenestrate, and occasionally of consider- 
able size. There is no evidence that the sporidia are ever 
excluded in the same manner as in Peziza, 
the lips closing over the disc so much as to 
prevent this. The diffusion of the sporidia 
probably depends on the dissolution of the 
asci, and hence they will not be widely 
dispersed, unless, perhaps, by the action of 
rain. 
In Tympanis, asci of two kinds have been 
observed in some species ; one kind contain- 
ing an indefinite number of very minute 
bodies resembling spermatia, and the other 
octosporous, containing sporidia of the usual 
type. 
The Spheriacei include an almost infinite variety in the form 
and character of the sporidia. Some of these are indefinite in 
the number contained in an ascus, although the majority are 
eight, and a few less. In the genera Torrubia and Hypocrea the 
structure differs somewhat from other groups, inasmuch as in 
the former the long thread-like sporidia break up into short 
joints, and in the latter the ascus contains sixteen subglobuse or 
Fie. 67.—Sporidium of 
Ostreichnion Americanum. 
