Vol. I] 



STEWART^LICHENS OF GALAPAGOS ISLANDS 433 



^ive. a distinct color to the vegetation of the transition region ; 

 Ld on Duncan Island above 500 ft. elevation, it occurs to such 

 an extent as to give the trees and shrubs on the upper par 

 of the island, when seen from a distance, the appearance of 

 being covered with a light green foliage, even during the dry 

 season, when they are out of leaf. Similar but less marked 

 conditions are found at Villamil, Albemarle Island, and on 



Tervis Island. , . ^ -i • 



Next to Alcctoria the Usncas are probably the most striking 

 of the fruticose forms, and the two species in the co lection, 

 U ceratina and U. longissima, were usually found m situations 

 similar to those of Alcctoria. In the transition region 

 they cover the branches of trees with 1°"^.^^^^°^"^; "f^^^^^^^^^^^ 

 sionally they are found in the moist regions. The greatest 

 display of Usncas is at Cowley Bay on the east side of Albe- 

 marle Island, where they occur abundantly above 1800 ft 

 elevation, mostly on branches of Biirscra gravcolcns Th s 

 tree in all. the regions where it occurs, seems to form a favorite 

 host (if I may use that tenii in this connection) for a consider- 

 able number of lichens, not only of fruticose, but of foliose and 



crustaceous forms as well. ,, ^- z? ^^,^ 



Of the three species of Ramalina m the collection, R com- 

 planata is usually found on the dryer parts of the islands 

 forming small tufts on dead sticks and twigs. R. farmacca 

 occurs where conditions are not so dry as in the last instance, 

 and sometimes even in the moist regions; while i?. ^'^^otdcs 

 occurs in both dry and moist situations. It was found on both 

 Barrington and Charles islands under very dry conditions, 

 and on Albemarle and Indefatigable islands, where conditions 



were moist. , . j • 4-u„ 



Both of the species of Rocclla collected were found m the 

 dry and lower transition regions. R. pcmcnsis occurs common^ 

 on bushes and small trees, forming tufts pendant from the 

 branches. There seems to be a great difference m the width 

 of the thallus in different specimens, especially toward the ends 

 of its branches. In some the branches are very slender, while 

 in others they are a millimeter in width near the tips. Ihe 

 second species. R. portcntosa, occurs almost exclusive y on 

 rocks It often forms large masses, especially m protected 

 places on the under side of projecting blocks of lava, where it 



