196 CHAPTERS ON FUNGI. [July, 



The various kinds of Truffles belong to this group, of which I 

 shall take, as the type, the genus Tuber. 



Tuber. 



Uterus closed, marbled with veins internally. Sporangia (asci) 

 pedicellate, confined to the veins. 



Tuber cibarium, Sibth. Common Truffle. Warty, black. 



Buried in the soil of woods, especially Beech- woods. 



Common in some parts of England, but generally rare. 



Forming rough, irregular, rounded bodies of 1 to 2 inches 

 (or more) in diameter, covered with small, sub-pyramidal warts. 

 Within white, marbled with darker veins. 



This is the common Truffle of this coimtry, and is now named 

 Tuber astivum. Attempts have been made to cultivate Truffles, 

 but hitherto without success. 



Suborder 3. Phacidiacei. 



Hymenium at length more or less exposed ; disc orbicular or 

 linear ; margin generally involute ; walls coriaceous. 



In this subdivision, the perithecium is generally of a hard or 

 cartilaginous nature, and often of an elongated form, and the 

 hymenium (or disc) is at first closed, and afterwards expands 

 more or less as the plant reaches maturity. The species gene- 

 rally grow on dead wood, or other vegetable substances. 



I shall instance the genera Hysterium and Rhytisma. 



.Hysterium. 



Perithecium elliptic or elongated, bursting by a simple longi- 

 tudinal fissure. 



The Hysteria are very nearly allied to the Lichens of the 

 genera Opegrapha and Graphis, but the want of a crust and of 

 green gonidia places them among the Fungi. 



Hysterium Fraxini, Pers. Ash-turf Hysterium. Erumpent, 

 elliptic, hard, black, lips tumid even, disc linear. — Grev. Sc. 

 Crypt. Fl. t. 72. 



On the smaller fallen branches of Ash. Winter and spring. 

 Common. 



A common species on Ash-branches, forming groups of small, 

 elliptic, black excrescences, sometimes arranged in a circular 

 manner. It is the Sphceria sulcata of the older botanists. The 

 asci are clavate, and the sporidia large, yellow, and fenestrate. 



