432 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



way in which this group of plants was treated, sixteen species 

 were found which had not before been reported from the islands, 

 and the range of quite a number of species already known was 

 considerably extended. There were, however, some fifteen 

 species reported by former expeditions to the islands, which 

 do not appear in my collection. Some of these have been 

 taken but once. 



I wish here to express my thanks to Dr. W. G. Farlow of 

 ■Harvard University for his kindness in making the identifica- 

 tion of the lichens in this collection — a task which, with my 

 limited knowlege of the subject, would have been impossible 

 for me. In the list of species which follows, bibliographic 

 references are omitted — it would have been too great a favor 

 to ask of Dr. Farlow to look them up. and I did not feel 

 competent to undertake it. 



In order to bring our knowledge of the lichenaceous flora 

 of these islands down to date, all species which have been 

 reported from them, but which escaped me in my collecting, 

 are included in the list. 



When one lands for the first time on almost any of the 

 islands, one is immediately struck with the great abundance 

 of lichens. This is true not only in the case of the larger 

 and higher islands, which reach sufficient elevation to receive 

 a considerable amount of moisture from the fog-banks which 

 strike their sides, and which consequently support a more or 

 less luxuriant vegetation ; but it is also true in the case of the 

 smaller and lower islands, where the amount of moisture 

 received throughout the greater part of the year is very scanty, 

 and where, in consequence, desert or semi-desert conditions 

 prevail. On islands of both sorts, lichens often lend a 

 striking appearance to the vegetation, the fruitcose forms 

 being the most important in this respect. Alectoria sarmentosa 

 is one of the most common of these. It is found largely in the 

 transition region*, where the branches both of trees and of 

 bushes are often heavily covered with masses of this rather 

 filmy species. On the south side of Indefatigable Island, it 



* For a discussion of the botanical regions of these islands, see Stewart: Proc. 

 Cal. Acad. Sci., 4th Sen, v. I, pp. 208-211. 



