396 INTBODTJCTION TO GEYPTOGAMIC BOTANY. 



thecia sunk in wartlike processes, so as to make an approach 

 to Trypethelium. The well-known Lichens which pass under 

 the name of Variolaria are mere degenerations of its species. 

 Porina differs from Pertusaria, in having only a single 

 perithecium in each pustule.* Stegobolus, Mont. (Fig. 82, d), 

 founded upon one of the Lichens collected by Cuming, in the 

 Philippine islands, is remarkable for throwing off a httle 

 lid from the top of the swellings formed by the perithecia. 

 When this has fallen, there is a white chalky disc, which 

 gradually breaks up together with the upper part of the peri- 

 thecium, exposing the hymenium. Thelotrema has the disc 

 at length naked, surrounded like Stictis by the lacerated 

 margin of the true perithecium, but there is no displacement 

 of a distinct hd, as in the former case. It is, in fact, exactly 

 analogous to Limboria, to which genus it might be referred, 

 save for its colourless perithecium. The genera are, for the 

 most part, cosmopolitan ; but a gTeat number of the crusta- 

 ceous species are peculiar to the tropics. Linear subtruncate 

 spermatia are figured by Tulasne, in Endocarpon sinopicum 

 and more minute and subfusiform in Pertusaria communis, 

 which is remarkarble for the'^^numerous strata in the epispore. 

 Spermatia of a subelliptic form, are also figured in S. minia- 

 tum and hepaticum. The sporophores in Pertusaria are 

 cylindrical ; in Endocarpon moniliform, cellular, or short and 

 oblong. E. sinopicum,, moreover, has myriads of sporidia ; 

 but, probably, another form of sporidia will eventually be 

 found similar to that of E. Tniniatum (Fig. 82, a), or E. lach- 

 neum (Fig. 81, c). 



5. SPHiEEOPHOEEI, Fr. 



Excipulum pale, not distinct from the stroma, at first entire, 

 then irregular, ruptured above. Thallus vertical, fruticulose. 



434. The branched and erect habit of the thallus of the 

 Lichens which belong to this group, induces a corresponding 

 change in the character of the fruit. The walls of the apo- 

 thecia are scarcely distinct from the stroma. "Were the thallus 

 reduced to a thin frond we should have nuclei scattered up and 



* Ascidium, Mont., differs in the same way from TrypetJoelimn. 



