682 THE SUBDIVISIONS OF THE VEGETABLE KINGDOM. 



but in the -spring give rise to their stromata, which consist of a number of orange- 

 coloured spherical bodies borne on purple stalks. A germinated Sclerotium is shown 

 in fig. 386 ^ The head bears the perithecia at its periphery (figs. 386 * and 386 % 

 and in these are contained the asci with their filamentous spores (figs. 386 ^' '^' ^). 



In addition to the forms enumerated above, a large number of pyrenomycetous 

 Fungi are found always associated with Algse into symbiotic communities known as 

 Lichens (cf. vol. i. p, 244). Though in a strict systematic review these forms should 

 be noted here, still, as Fungi from at least two other groups occur in similar 

 relations to Algge, it will be convenient to treat them all under one heading, rather 

 than scattered over the alliances with which they have a natural affinity (see 

 Lichenes, p. 691). 



Discomiycetes. — These, like the Pyrenomycetes, constitute a very extensive 

 family. They are characterized by the fact that when mature the structure bearing 

 the asci expands into a disc or cup, so that the ascal surface is exposed ; or this 

 surface is spread over the outside of a fleshy receptacle. 



As a good example of a Discomycete, the large genus Peziza may be cited. 

 They are met with chiefl}^ on decaying vegetable matter, and in the various species 

 the disc or cup — the fertile receptacle — is sessile on the mj^celium. Peziza vesi- 

 culosa {cf. fig. 388^) is one of the commonest British species, occurring in humus, 

 rotting leaves, &c. Its cups (the apothecia) attain a diameter of 2-3 inches, are 

 buff" in colour, fleshy, and very fragile. The inside of the receptacle is everywhere 

 lined with the layer of asci. with sterile hairs, the paraphyses, between (it is similar 

 to fig. 388'^). Another common species is P. scutellata; it forms little flat red discs 

 about the size of sixpenny-pieces upon rotting wood, and the margin is set with 

 hairs. Several of the Pezizas are stalked (cf. figs. 388^ and 388*). P. ceruginosa 

 is an interesting form; it also is stalked, and grows especially upon dead branches of 

 Oak. It permeates the wood with its mycelium, and this appears to excrete a green 

 pigment which stains the wood in its vicinity. The stalked apothecium is also 

 green in colour. This green-rotting wood is exceedingly common and is used in 

 the manufacture of "Tunbridge ware"; the actual Fungus, however, is by no means 

 so obvious, and from the majority of green-rotted branches not only has the apothe- 

 cium disappeared, but the mycelium also. Resembling a Peziza, but very gelatinous, 

 is Bulgaria inquinans, common on decaying trunks of trees. Peziza WillkoTnmii, 

 causing the Larch-canker, has been already referred to (cf. p. 522). Nearly related 

 to the Pezizas, and causing parasitic diseases of plants, is Sclerotinia. It possesses 

 a well-marked Sclerotium, from which stalked Peziza-like apothecia are produced. 

 A species not uncommon in this country is Sclerotinia tuherosa. It attacks the 

 underground parts of Wood Anemones and forms its sclerotia in the tubers of this 

 plant. In the spring, instead of Anemone-flowers coming up, the Sclerotium gives 

 rise to a number of long-stalked apothecia which appear just above the surface of 

 the ground. 



Other more complex Discomycetes are the Helvellas and Morels, forms purely 

 saprophytic. Helvella produces a stalked receptacle, curiously folded ( see figs. 388 ^ 



