330 SYSTEMATIC 



The fruits are coloured yellowish, brown or red (or dark and carbonaceous 

 in Pilophorus), and are borne on the tips of the branches or on the margins 

 of the scyphi. In Glossodium and Thysanot/ieaum\.\\e former from New 

 Granada, the latter from Australia the apothecia occupy one side of the 

 widened surface at the tips. 



Cephalodia are developed on the primary thallus of Pilophorus, and on 

 the podetia of Stereocaulon and Argopsis. 



Podetia simple, short, not widening upwards. 

 Podetial stalks naked. 



Primary thallus thin, continuous i. Gomphillus Nyl. 



Primary thallus granular or squamulose ... 2. Baeomyces Pers. 

 Primary thallus foliose. 



Podetia superficial 3. *Heteromyces Mull.-Arg. 



Podetia marginal 4. *Gymnoderma 1 Nyl. 



Podetial stalks granular, squamulose 5. Pilophorus Th. Fr. 



Podetia short, widening upwards. 



Podetia simple above, rarely divided ... 6. *Glossodium Nyl. 



Podetia lobed, leaf-like 7. *Thysanothedum Berk. & Mont. 



Podetia elongate, variously branched, or scy-1 , 



\ 8. Cladoma Hill, 

 phous and hollow J 



Podetia elongate, not scyphous, the stalks solid. 



Spores elongate, septate 9. Stereocaulon Schreb. 



Spores muriform 10. *Argopsis Th. Fr. 



XXXIV. GYROPHORACEAE 



A small family of foliose lichens allied to Lecideaceae by the character 

 of the fruit a superficial apothecium in the formation of which the gonidia 

 take no share. There are only three genera, distinguished by differences in 

 spore and other characters. Dermatiscum has light-coloured thallus and 

 fruits ; of the two species, one occurs in Central Europe, the other in North 

 America. Umbilicaria and Gyrophora are British ; they are dark-coloured 

 rock-lichens and are extremely abundant in Northern regions where they 

 are known as "tripe de roche." Algal cells Protococcaceae. 



Umbilicaria, Dermatiscum, and some species of GyropJiora are attached 

 to the substratum by a central point. Other species of Gyrophora are 

 rhizinose. In all there is a cortex of plectenchyma above and below. In 

 Gyrophora the thallus may be monophyllous as in Umbilicaria, or poly- 

 phyllous and with or without rhizinae. New lobes frequently arise from 

 protuberances or warts on the older parts of the thallus. At the periphery, 

 in most species, growth is equal along the margins, in G. erosa* the edge is 

 formed of numerous anastomosing lobes with lateral branching, the whole 

 forming a broadly meshed open network. Further back the tissues become 

 continuous owing to the active growth of the lower tissue or hypothallus, 



1 Neophyllis Wils. is synonymous with Gynmoderma. 2 Lindau 1 899. 



