FAMILIES AND GENERA 325 



XXIII. Lecanactwaceae 



By many systematists this family is included under Graphidineae on 

 account of the fruit structure which in some of the forms is carbonaceous 

 and almost lirellate, and also because the algal symbiont is Trentepohlia. 

 The thallus is primitive, being thinly crustaceous and non-corticate ; the 

 apothecium has a black carbonaceous hypothecium in two of the genera, 

 Lecanactis and Schismatoinma {Platygraphd); in the third genus, Melaiii- 

 pydium, it is colourless. The latter is monotypic, and the spores become 

 muriform. In the other genera they are elongate and multi-septate. 



Apothecia with prominent proper margin i. Lecanactis Eschw. 



Apothecia with thin proper margin 2. *Melampydium Miill.-Arg. 



Apothecia with thalhne margin _ 3. Schismatomma Flot. 



XXIV. PiLOCARPACEAE 



A small family with but one genus, PilocM'pon. It is distinguished as 

 one of the few epiphyllous genera of lichens associated with Protococcaceous 

 gonidia and with a distribution extending far beyond the tropics. The best 

 known species, P. leucoblepJmrum, encircles the base of pine-needles with 

 a white felted crust, or inhabits coriaceous evergreen leaves. Another species 

 lives on fern leaves. The fruit is a discoid apothecium with a dark carbona- 

 ceous hypothecium and proper margin, and with a second thalline margin. 

 The paraphyses are branched and interwoven above. 



Spores elongate, Srseptate, colourless i. Pilocarpon Wain. 



XXV. Chrysotrichaceae 



This family now, according to Hue^ includes two genera, Crocynia and 

 Chrysothrix. In both there is a thallus of interlaced hyphae with Protococ- 

 caceous algae scattered through it or in groups. The structure is thus 

 homoiomerous, and Hue has suggested for it a new series, "Intertextae." 

 The only British species, Crocynia lanuginosa, first placed by Nylander^ in 

 Amphiloma and later transferred bj' him to Leproloma^, has a soft crustaceous 

 lobate thallus, furfuraceous on the surface; no fructification has been found. 

 A West Indian species, C. gossypina, has discoid apothecia with a thalline 

 margin. There is only one species of Chrysothrix, Ch. nolitangere, which 

 forms small clumps or tufts on the spines of Cactus in Chili. The structure 

 is somewhat similar to that of Crocynia. 



Spores colourless, simple i. Crocynia Nyl. 



Spores colourless, 2-3-septate 2. *Chrysothrix Mont. 



' Hue 1909. - Nylander 1855. ' Nylander 1883. 



