3i8 SYSTEMATIC 



XL Mycoporaceae 

 A small family with only two genera which are found in both Hemi- 

 spheres ; 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 .--i. 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 Miill.-Arg. and L. coccophora 

 Hue. The latter has been recently examined by Hue' who finds, on the 

 thalli, cephalodia which are peculiar in containing bright-green gelatinous 

 algae either Urococcns 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 i. *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 {Phyllactidiuni). 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 i. *Strigula Fries. 



Thallus irregular. 



Perithecia without hairs. 

 Spores colourless. 



Spores elongate, multi-septate 2. *Phylloporina Miill.-Arg. 



Spores muriform 3. *Phyllobathelium Miill.-Arg. 



Spores brown. 



Spores simple 4. *Haplopyrenula Miill.-Arg. 



Spores elongate, r-3-septate 5. *Microtheliopsis Miill.-Arg. , 



Perithecia beset with stiff hairs 6. *Trichothelium Miill.-Arg. 



' Hue 1905. 



