FAMILIES AND GENERA 317 



superficial or embedded. The genera are arranged according to spore 

 characters : 



Spores elongate, 2- or more-septate. 



Spore cells cylindrical, colourless I. *Pleurotrema Miill.-Arg. 



Spore cells globose-Ientiform. 



Spores colourless 2. *Plagiotrema Miill.-Arg. 



Spores brown 3. *Parathelium Miill.-Arg. 



Spores muriform. 



Spores colourless 4. *Campylothelium Miill.-Arg. 



Spores brown 5 . *Pleurotheli um Miill.-Arg. 



IX. Trypetheliaceae 

 This and the following two families are distinguished by the pseudo- 

 stroma or compound fruit, a character rare among lichens, though the true 

 stroma is frequent in Pyrenomycetes in such genera as Dothidea, Vaha, etc. 

 The genera are crustaceous and corticolous and occur with few exceptions 

 iti tropical or subtropical regions, mostly in the Western Hemisphere. 

 Several grow on officinal bark {Cinchona, etc.). Algal cells are Trentepohlia. 

 As in many tropical lichens, the spores are large. The genera are based 

 chiefly on spore characters, on septation, and on the form of the spore 

 cells : 



Spore cells cylindrical or cuboid. 



Spores colourless, elongate, multi-septate I. *Tomasiella Miill.-Arg. 



Spores colourless, muriform 2. *Laurera Rehb. 



Spores brown, muriform 3. *Bottaria Massal. 



Spore cells globose-Ientiform. 



Spores colourless, elongate, multi-septate 4. *Trypethelium Spreng. 



Spores brown, elongate, multi-septate 5. Melanotheca Miill.-Arg. 



X. ASTROTHELIACEAE 



The perithecia are either upright or inclined, and occur usually in 

 radiate groups. They are free or united in a stroma, and the elongate 

 ostioles open separately or coalesce in a common canal. The genera are 

 all crustaceous, with Trentepohlia gonidia. They are tropical or subtropical, 

 mostly in the Western Hemisphere; but species oi Parmentaria and Astro- 

 thelium have been recorded also from Australia. 



The spores are all many-celled and the form of their cells is a generic 

 character : 



Spores elongate, multi-septate. 



Spore cells cylindrical i. *Lithothelium Mull.-Arg. 



Spore cells globose-Ientiform. 



Spores colourless 2. *Astrothelium Trev. 



Spores brown 3- *Pyrenastrura Eschw. 



Spores muriform. 



Spores colourless 4- *Heufleria Trev. 



Spores brown 5- *Parmentaria F^e. 



