LICHENES — DR JEAN MULLER. 343 



ASGOMYCETES. 



LICHENES. 



By De JEAN MULLER of GENEVA. 



The lichen-flora of Socotra, so far as is known at the present time, contains 

 130 species with several varieties, belonging to 47 genera and 14 tribes. Of the 

 species more than one half (69) or 53 per cent, are new to science, a fourth are 

 exclusively species of the warmer regions of the globe, whilst the remaining 

 fourth includes species found also in Europe. The tropical and subtropical 

 species thus constitute three-fourths of the whole lichen- flora. 



The genera of crustaceous lichens are best represented. Opegrapha, Buellia, 

 Pertusaria, and Parmelia exhibit the greatest number of species, the first three 

 being especially remarkable on account of their relatively large proportion of 

 new species. On the other hand, there is to be noted a great poverty or absence 

 of species of Splicer ophor on, Cladonia, Stereocaulon, Usnea, Cetraria, Gyro- 

 phora, Peltigera, Sticta, Stictina, Pannaria, Thelotrema, and Ocellularia, genera 

 of Verrucariacese, which for the most part require a warm and moist climate, 

 can hardly therefore be expected to occur in any great abundance on the arid 

 rocky land of Socotra. 



The whole lichen-flora is consequently very different in character from that 

 of Madagascar, the Mascarene and Sunda Islands, and has the greatest analogy 

 with that of the ^Egyptian deserts. 



I may add, that in the investigation of the lichen-flora of Socotra, as in all 

 my other examinations of lichens, I have not used the so-called chemical tests 

 for the differentiation of species, as I regard " chemical species " — forms which 

 differ from one other in no way save in chemical reaction,— as having no natural 

 and scientific foundation. The variation in reaction is entirely physiological, 

 dependant upon complex conditions of nutrition, and is of no systematic value 

 in the discrimination either of species or of varieties. 



Order I. COLLEMACE.E. 



Collemaeece, Mull. Arg. Lich. Geneve, 80. 

 Collemacei, Nyl. (Essai 163 sine charact.) Syn. 88. 

 Phycoliclunes, Mass. Sched. crit. 139 (sine charact). 



Tribe 1. Omphalarie^e. 



Omphalariece, Miill. Arg. Lich. Geneve 31 ; Stitzb. Beitr. 143 pr. p. 

 Collemei, Nyl. Essai 163 pr. p.; Syn. 93 pr. p. 

 Eucollemei, Tuck. Gen. xii. pr. p. 



