328 SYSTEMATIC 



Thallus with Trentepholia gonidia. 

 Asci 6-8-spored. 



Spores simple 2. Jonaspis Th. Fr. 



Spores i-septate 3. *MicrophiaIe A. Zahlbr. 



Spores septate or muriform 4. Gyalecta Ach. 



Asci 1 2-many-spored. 



Spores i-septate 5. *Ramonia Stizenb. 



Spores fusiform or acicular, many-septate ... 6. Pachyphiale Ldnnr. 

 Apothecia carbonaceous. 



Spores elongate, 2-3-septate 7. *Sagiolechia Massal. 



XXX. COENOGONIACEAE 



There are only two genera in this small family, Coenogoniuin with Trente- 

 pohlia gonidia, and Racodiuin with Cladophora. Both genera follow the algal 

 form and are filamentous. In Coenogoniuin the filaments are sometimes 

 matted into a loose felted expansion. The genus is mainly tropical or 

 subtropical and mostly rather light-coloured. There is only one British 

 species, C. ebeneiun', a sterile form, in which the hyphae are very dark-brown ; 

 it often covers large areas of stone or rock with its sooty-like creeping 

 filaments. 



Racodium includes 2 (?) species. One of these, R. rupestre, is sterile and 

 resembles C. ebeneuui in form and colour. 



The apothecia of Coenogoniuin are waxy and light-coloured ; they are 

 borne laterally on the filaments; the spores are simple or i -septate. 



Thallus with Trentepohlia goniA\3. r. Coenogonium Ehrenb. 



Thallus with C/rt^i3^;^onz gonidia 2. Racodium Fr. 



XXXI. Lecideaceae 



One of the largest lichen families as' regards both genera and species, 

 and of world-wide distribution. The algal cells are Protococcaceae. The 

 thallus is mostly crustaceous but it becomes squamulose in Psora, a section 

 of Lecidea; and in Sphaerophoropsis, a Brazilian genus, there are small 

 upright fronds or stalks with lateral apothecia. The prevailing colour of 

 the thallus is some shade of grey, but it ranges from white or yellow to 

 dark-brown or almost black. Cephalodia appear in some of the species. 



The apothecia have a proper margin only, no gonidia taking part in the 

 fruit-formation. They may be soft and waxy (biatorine) or hard and 

 carbonaceous (lecideine). The genera are mainly based on spore characters 

 which are very varied. 



The arrangement of genera given below follows that of Zahlbruckner ; 

 in several instances, both as to the limitations of genera and to the nomen- 

 clature, it differs from that of British text-books, though the general principle 

 of classification is the same. 



' Lorrain Smith 1906. 



