Origin of California Lichen F'lora. 215 



SUGGESTIONS AS TO THE ORIGIN OF CALIFORNIA'S 



LICHEN FLORA. 

 By Albert C. Herre. 



Even a cursory examination of Tuckeiman's monumental 

 works on North American lichens gives one the impression that 

 the lichen flora of California is very remarkable. A study of 

 California lichens in field and laboratory for the past nine years 

 has heightened this impression and convinced me that it is un- 

 usual in several respects. 



In the first place, we find in California a considerable num- 

 ber of lichens characteristic of other regions, but occurring 

 rarely or not at all in other parts of the United States, while, 

 as a contrast to this, certain species which are abundant ahnost 

 everywhere else in our country are here conspicuous by their 

 absence. Lastly we have here an extraordinary number of 

 lichens found nowhere else. 



As examples of lichens common to the Pacific coast and other 

 parts of the world, but not found in the rest of the United States, 

 we may cite from among many the following: Cyphelium 

 inquinans, Calicium hyperellum, Arthopyrcnia halodytes, Micro- 

 thelia victzleri, Opegrapha saxicola, Cetraria chlorophylla, Lecidea 

 quernca, Lecidea caulescens, Lecidea intumescens, Lecidea aro- 

 matica, Gyrophora polyrrhiza, Leptogium palmatum, Polychidium 

 alhociliatum, Rinodina conradi, Pertusaria amara, and many 

 other European forms; Buellia halonia, a Cape of Good Hope 

 species; three species of Roccella, juciformis, tinctoria, and 

 jucoides, all occur on the coast of California and are widely 

 distributed over the wanner maritime regions of the earth, but 

 are unknown to the Gulf or South Atlantic states. Dirina, a 

 maritimie genus represented in Europe and on the warmer coasts 

 generally, does not occur along the shores of the eastern states, 

 though represented in California by three endemic species. Then 

 there are other lichens which are widely distributed in the Old 

 world, yet occur to a very limited extent over most of the United 

 States, though reaching great size and fruiting luxuriantly in 

 California; as an example of such we may name Leiharia vulpina. 



Among the most widely distributed of lichens are the three 

 closely allied species of Cladonia, rangiferina, alpeslris, and 



