CLASSIFICATION. 77 
examined more in detail. The Twuberacei, or subterranean 
Ascomycetes, are analogous to the Hypogai of the Gasteromycetes. 
The truffle is a familiar and highly prized example. There is a 
kind of outer peridium, and the interior consists of a fleshy 
hymenium, more or less convoluted, sometimes sinuous and con- 
fluent, so as to leave only minute elongated and irregular cavi- 
ties, and sometimes none at all, the two opposing faces of the 
hymenium meeting and coalescing.* Certain privileged cells 
of the hymenium swell, and ultimately become asci, enclosing a 
definite number of sporidia. The sporidia in many cases are 
large, reticulated, echinulate or verrucose, and mostly somewhat 
globose. In the genus Elaphomyces, the asci are more than 
commonly diffluent. 
The L£lvellacei are fleshy in substance, or somewhat waxy, 
sometimes tremelloid. There is no peridium, but the hymenium 
is always exposed. There is a great variety of forms, some 
being pileate, and others cup-shaped, as there is also a great 
variation in size, from the minute Peziza, small as a grain of 
sand, to the large Helvella gigas, which equals in dimen- 
sions the head of a child. In the pileate forms, the stroma 
is fleshy and highly developed; in the cup-shaped, it is 
reduced to the external cells of the cup which enclose the 
hymenium. The hymenium itself consists of elongated fertile 
cells, or asci, mixed with linear thread-like barren cells, called 
paraphyses, which are regarded by some authors as barren asci. 
These are placed side by side in juxtaposition with the apex 
outwards. Each ascus contains a definite number of sporidia, 
which are sometimes coloured. When mature, the asci explode 
above, and the sporidia may be seen escaping like a miniature 
cloud of smoke in the light of the mid-day sun. The dise or 
surface of the hymenium is often brightly coloured in the genus 
Peziza; tints of orange, red, and brown having the predominance. 
In Phacidiacei, the substance is hard and leathery, intermediate 
between the fleshy Hlvellacei and the more horny of the Sphe- 
riacet. The perithecia are either orbicular or elongated, and the 
* Tulasne, L. R. and C., ‘‘ Fungi Hypogei,” Paris; Vittadini, C., ‘ Mono- 
graphia Tuberacearum,” Milan, 1831. 
