it was noted that Ktaadn is one solid mass of granite. With 

 such a vast rock exposure, it offers an admirable opportunity for 

 the genetic study of this type of society. It is on the higher 

 peaks, the crest, and the upper talus slopes, where vegetation has 

 yet been unable to encroach, that we may best study the pioneer 

 plant society. 



(a). The Crustaceans Lichen Society. Along the crest, 

 where frost action splits the red granite into vast blocks which, 

 losing their perpendicularity, still remain as oblique projecting 

 plates in chaotic desolation, we find the bare rocks with only a 

 crustaceous lichen covering. The most abundant and pioneer 

 form is Buellia geographic a, of universal distribution. With 

 its yellowish- green cast it gives a tone most lurid to the vast talus 

 slopes and weathered crest. The growth of Buellia, as well as 

 other forms, is centripetal and as the lichen expands in circum- 

 ference it dies behind at the center, becoming black. There are 

 several other less prominent associated forms. 



Beginning in small patches these crustaceous lichens expand 

 into mats and mats into islands as it were. Finally uniting they 

 may cover entire boulders. Needing no soil the crustaceous 

 lichen is essentially a lithophyte. To fit it to this extremely 

 xerophytic and precarious life, it must first be able to form an 

 attachment to the rock upon which it lives and secondly it must 

 have ability to obtain food from its rock substratum the air. By 

 means of holdfasts its position is secured. From rain and drain- 

 age various compounds may be absorbed. Again the symbiosis 

 of fungus and alga in the lichen perhaps fits it as a pioneer form. 

 Finally the ability to dry up and suffer no injury, reviving 

 with the next rain, admirably fits the lichen to its xerolithophytic 

 life. .Several foliaceous forms may accompany this crustaceous 

 covering. Umbilicarias are not uncommon even at the very 

 summit, yet they never become conspicuously prominent. 

 Upon this lichen mat, and even upon the bare rocks, occur sev- 

 eral species of lithophytic mosses. Andre cea petrophila, Rhaco- 

 mitrium sudeticum and R. aciculare may be mentioned. 



The wash, decay, and disintegration from the lichen-moss- 

 mat lodging in angles where rocks adjoin, in cracks, crevices, or 

 niches, gradually form a slight soil and prepare the way for 



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