XXIV. Pilocarpaceae
A small family with but one genus, Pilocarpon. 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. leucoblepharum, 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 carbonaceous hypothecium and proper margin, and with a second thalline margin. The paraphyses are branched and interwoven above.
| Spores elongate, 3-septate, colourless | 1. | Pilocarpon Wain. |
XXV. Chrysotrichaceae
This family now, according to Hue[1047], includes two genera, Crocynia and Chrysothrix. In both there is a thallus of interlaced hyphae with Protococcaceous 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[1048] in Amphiloma and later transferred by him to Leproloma[1049], 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 | 1. | Crocynia Nyl. |
| Spores colourless, 2-3-septate | 2. | *Chrysothrix Mont. |
XXVI. Thelotremaceae
A tropical or subtropical family of which the leading characteristic is the deeply sunk disc of the apothecium: it has a proper hyphal margin, and, round that, an overarching thalline margin. The apothecia occur singly, or they are united in a kind of pseudostroma: in Tremotylium several grow together, while in Polystroma each new apothecium develops as an outgrowth from the thalline margin of the one already formed, so that an upright, branching succession of fruits is built up. It is a very unusual type of lichen fructification, with one species, P. Ferdinandezii, found in Spain and in Guiana.
The thallus in all the genera is crustaceous with an amorphous (decomposed) cortex; or it is non-corticate. The algal cells are Trentepohlia except in Phyllophthalmaria, an epiphyllous genus associated with the alga Phycopeltis. In Polystroma the alga is unknown.