DISCOMYCETES. 241 



The paraphyses are developed from the mycelium of the 

 €nvelope and occupy the interior of the aseocarp, while the 

 asci arise later from the ascogenous hyphae and force their way 

 in. The formation of asci and paraphyses may go on for a 

 long time. Periphyses are not produced. 



The Discomycetes include five divisions, the Phacidiaceae, 

 JStictideae, Tryhlidieae, Dermateaceae, and Pezizeae. Many of 

 the species included in these are parasitic on cryptogamic 

 plants to form lichens, the majority are saprophytes, and only 

 a few isolated groups are true parasites on higher plants. The 

 latter belong to the Phacidiaceae, Dermateaceae, and Pezizeae. 



(1) PHACIDIACEAE 



The apothecia are black and thick- walled, at first embedded 

 in their substratum, but later breaking through it. The asco- 

 genous layer is spread out on a delicate flat hypothecium. 

 The black apothecia of the species of Phacidiuni are frequent 

 on leaves and needles. Eehm divides the group into two 

 fanulies : the Euphacidieae and the Pseudopliacidieae. 



EUPHACIDIEAE. 



The apothecia are embedded in the tissues of the host ; the 

 superincumbent layers of the substratum forming over them a 

 blackish membranous plate, which is ruptured into lobes and 

 -exposes the black apothecial disc. 



Phacidium. 



The apothecia are fused with the superincumbent layers of 

 the host-plant, and the black cover so formed is split into 

 -several lobes. The club-shaped asci contain eight colourless, 

 unicellular, ovoid or spindle-shaped spores. The paraphyses 

 are filamentous. The pore of the ascus is coloured blue by 

 iodine. 



Phacidium repandum Fr. (Britain). Occurs on living leaves 

 and stems of Asperula odorata, Galium mollugo, and other 

 Rubiaceae. The pycnidial form is probably Phyllachora 

 j)unctiformis Fr. 



Q 



