NEW ENGLAND LICHENS 40 



buildings, and not uncommonly on rocks. The trees of the 

 New England apple orchards are conspicuously decorated 

 with them. 



Distribution: Common throughout New England in 

 the Austral and Transition zones, occuring perhaps less 

 commonly in the Canadian, and absent, so far as I have 

 observed, in the Hudsonian as represented in these States. 

 Its presence, on other than tree substrata, seems due, how- 

 ever, to dissemination from tree-plants as in tree-less regions, 

 i. e., above timber line, the lichen does not occur, except 

 accidentally. The distribution of tree-living species to varied 

 substrata beneath, is commonly met with in many species. 



Life History: Of all the many and varied species of 

 lichens that are common to New England, there is perhaps no 

 one so conspicuous as the present species, due to three rea- 

 sons : first its widespread abundance throughout the zones, 

 secondly its large size, and thirdly its fresh green color. 

 From the degenerate and struggling examples of the city 

 environs,* to the perfect and fresh specimens of the primeval 

 forest, it has a certain constancy of character that makes it 

 easily recognizable, and known to all who pay the least at- 

 tention to their natural surroundings. Yet it teaches the 

 scientific spirit of careful observance, so varied often is its 

 habit, owing mainly to the character of substratum, and the 

 position of growth. For example, a specimen growing on a 

 rock, or on the comparatively smooth and dark colored bark 

 of the young White Pine {Pinus strobus L. ) or Paper Birch 

 {Betula papyri f era Marsh) not only develops into a nearly 

 perfect, circular mat of green, the thallus lobes and structure 

 symmetrical and normal, but it is also set off by its dark or 

 light background so that all its beauty is exhibited in clear 

 relief. (See Fig. 3.) 



"The round, greenish-yellow lichens on the white-pines 

 loom through the mist like shields whose devices you would 

 fain read." 



• Due to the presence of sulphur dioxide in the atmosphere. 



