VI. Mastoideaceae
A family containing one genus and one species, with a wide distribution, having been found in Siberia, on the Antarctic continent (Graham’s Land), as also in Tierra del Fuego, South Georgia, South Shetland Islands and Kerguelen. The thallus is foliose, of small thin lobes, and without rhizinae. Algal cells Prasiola[1040]. The perithecia are globose and partly project from the thallus; the asci are 8-spored; the paraphyses are mucilaginous and partly dissolving.
| Spores elongate-fusiform, simple, colourless | 1. | *Mastoidea Hook. and Harv. |
VII. Pyrenulaceae
This family of crustaceous lichens differs from Verrucariaceae chiefly in the gonidium which is a species of Trentepohlia. Genera and species are largely corticolous and the thallus is inconspicuous, often developing within the substratum. The perithecia, like those of Verrucariae, are immersed or partly emergent and have an entire or dimidiate outer wall. They are scattered over the thallus except in Anthracothecium where they are often coalescent. This genus is tropical or subtropical except for one species which inhabits S.W. Ireland.
Paraphyses are variable, and in some species tend to disappear, but do not dissolve in mucilage. The spores are generally colourless, only in one monotypic genus, Coccotrema, are they simple. The cells into which the spore is divided differ in form according to the genus.
| Paraphyses branched and entangled or wanting. | ||
| Perithecia opening above by stellate lobes | 1. | *Asteroporum Müll.-Arg. |
| Perithecia opening by a pore. | ||
| Spores variously septate. | ||
| Spore cells cylindrical or cuboid. | ||
| Spores colourless, elongate or ovate 1-5-septate | 2. | Arthopyrenia Massal. |
| Spores colourless, filiform 1-multi-septate | 3. | Leptorhaphis Koerb. |
| Spores colourless, muriform | 4. | Polyblastropsis A. Zahlbr. |
| Spores brown, ovoid or elongate 2-5-septate | 5. | Microthelia Koerb. |
| Spore cells globose or lentiform, 3-multi-septate | 6. | *Pseudopyrenula Müll.-Arg. |
| Paraphyses unbranched free. | ||
| Spore cells cylindrical or cuboid. | ||
| Perithecia beset with hairs | 7. | *Stereochlamys Müll.-Arg. |
| Perithecia naked. | ||
| Asci disappearing; spores elongate multi-septate, colourless | 8. | *Belonia Koerb. |
| Asci persistent. | ||
| Spores simple, ellipsoid, colourless | 9. | *Coccotrema Müll.-Arg. |
| Spores elongate, 1-multi-septate, colourless | 10. | Porina Müll.-Arg. |
| Spores elongate, 1-multi-septate, brown | 11. | Blastodesmia Massal. |
| Spores muriform, colourless | 12. | *Clathroporina Müll.-Arg. |
| Spores elongate, 2-3-septate, colourless | 13. | Thelopsis Nyl. |
| Spore cells globose or lentiform. | ||
| Spores elongate, 1-5-septate, brown | 14. | Pyrenula Massal. |
| Spores muriform, brown | 15. | Anthracothecium Massal. |
VIII. Paratheliaceae
This family is peculiar in that the perithecia open by a somewhat elongate ostiole that slants at an oblique angle. The algal cells are Trentepohlia. Genera and species are endemic in tropical or subtropical regions of the Western hemisphere, though a species of Pleurotrema has been found in subantarctic America. They are corticolous and the thallus is either superficial or embedded. The genera are arranged according to spore characters: