A small family with only two genera which are found in both Hemispheres; species of both occur in Great Britain. They are all corticolous. The perithecia are united into a partially chambered fruiting body surrounded by a common wall, but opening by separate ostioles. The thallus is thinly crustaceous, with Palmella gonidia in Mycoporum, and Trentepohlia in Mycoporellum. The spores are colourless or brown in both genera:
| Spores muriform | 1. | Mycoporum Flot. |
| Spores elongate, multi-septate | 2. | Mycoporellum A. Zahlbr. |
XII. Phyllopyreniaceae
Thallus foliose with both surfaces corticate and attached by rhizinae. Algal cells Trentepohlia. There is but one genus, Lepolichen, which has a laciniate somewhat upward growing thallus. Two species, both from South America, have been described, L. granulatus Müll.-Arg. and L. coccophora Hue. The latter has been recently examined by Hue[1041] who finds, on the thalli, cephalodia which are peculiar in containing bright-green gelatinous algae either Urococcus or Gloeocystis, one of the few instances known of chlorophyllaceous algae forming part of a cephalodium. Gloeocystis may be the only alga present in the cephalodium; Urococcus is always accompanied by Scytonema.
The perithecia are immersed in thalline tubercles:
| Spores colourless, simple, ovoid or ovoid-elongate | 1. | *Lepolichen Trevis. |
XIII. Strigulaceae
A family of epiphyllous lichens inhabiting and disfiguring coriaceous evergreen leaves, or occasionally fern leaves in tropical or subtropical regions. The algae associated are Mycoidea and Phycopeltis (Phyllactidium). The only truly parasitic lichen, Strigula, belongs to this family: the alga precedes the lichen on the leaves and is gradually invaded by the hyphae of the lichen and altered in character. The small black perithecia are scattered over the surface. In Strigula the lichen retains the spreading rounded form of the alga. The other genera are more irregular.
| Thallus orbicular in outline | 1. | *Strigula Fries. |
| Thallus irregular. | ||
| Perithecia without hairs. | ||
| Spores colourless. | ||
| Spores elongate, multi-septate | 2. | *Phylloporina Müll.-Arg. |
| Spores muriform | 3. | *Phyllobathelium Müll.-Arg. |
| Spores brown. | ||
| Spores simple | 4. | *Haplopyrenula Müll.-Arg. |
| Spores elongate, 1-3-septate | 5. | *Microtheliopsis Müll.-Arg. |
| Perithecia beset with stiff hairs | 6. | *Trichothelium Müll.-Arg. |