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or 4 mm. wide, but is more likely to be met in a dwarfed or strag- 

 gling state. The often short branches 1 or 2 mm. wide, may broaden 

 abruptly to twice that width at the neatly rounded, often lifted tips. 

 The upper surface is chestnut brown to pale purplish brown, but 

 appears whitish because of the many white, mealy particles 0.01 or 

 0.02 mm. across, distributed rather regularly, and plainly visible 

 under the lens. At times these particles appear only on small areas 

 near the tips. At other times they whiten the entire lichen, so that 

 the brown color can hardly be seen. Tiny whitish lobes and granules 

 may cover the entire lichen, and there may be soredia. The under 

 surface at the tips is whitish, elsewhere blackening, with black root- 

 like holdfasts. 



Fruits locally rare, up to 5 mm. across, brown or frosted white, 

 with a rim which may be smooth, lumpy or lobed. Spores 2-celled, 

 brown, 23 to 40 by 12 to 21 microns. 



Physcia pulverulenta is marked from all other local Papery 

 Lichens by the white particles on the brown upper surface. In speci- 

 mens where the particles are few or lacking, the coloring is usually 

 dark, but some at least of the tips whitish beneath, a rather unusual 

 combination. The tiny lobes seen on some specimens are short and 

 obtuse. No further comparisons are needed to determine the normal 

 form, but sometimes the brown surface is very pale, nearly white, 

 when it approaches P. graniilifcra, a species found further west. 

 At first glance it might be mistaken for a form of P. stellaris. 



Physcia adglutinata. Clinging Blister Lichen 



Occurring in the New York area, but not common, and so in- 

 conspicuous that it escapes attention. It grows on tree-bark in 

 rosettes commonly 2 or 3 cm. across, but inclined to fall away and 

 disintegrate, or to remain so undeveloped as often to resemble a 

 Crust Lichen, with no visible papery structure. The central parts 

 are nearly always crust-like with tiny lobes 0.1 mm. across or nar- 

 rower, barely emerging here and there, or merely etched on the 

 crust, becoming evident where it cracks into irregular patches 1 to 

 2 mm. across, where they show on the free edges. Papery branches 

 and lobes tissue-thin are seen at the edge of the rosette, glued tight 

 against the bark, and vaguely dividing into parts about 1 mm. 



