202 



grooved beneath. Upper surface whitish to pale gray ; under surface 

 pale. 



Fruits rather frequent, up to 0.5 mm. in diameter, blackish, 

 with a pale rim, which may be smooth or bear granules and soredia. 

 Spores 2-celled, blackish, 11 to 17 by 5 to 9 microns, usually near 

 the minimum. 



Physcia teretiuscula, as seen in the New York area, is the 

 smallest of the genus, one of the smallest of Papery Lichens, requir- 

 ing close examination with a lens to see its parts. Most nearly 

 allied to P. trihacia, it differs in lying perfectly flat, with margins 

 curled down, and in the spores, which are commonly smaller than 

 any other local species of Physcia. Especially distinctive are the 

 granules and soredia on the fruit-rims, for no similar lichen has 

 them. This species is smaller than P. Frostii, with narrower and 

 more pointed parts, and is much more often found bearing its very 

 different fruits. Crocynia sonata (Group 14) is often as small, 

 but much darker, and marked with zones of its pale tips. The 

 rarity of P. teretiuscula helps to distinguish it from P. trihacia and 

 Crocynia sonata, both common. The form differs somewhat from 

 that originally named in Europe, but this name seems to be the 

 best one for it. 



Physcia hispida. Hood Lichen 



Also called P. tenella or in part P. ascendens. Found occasion- 

 ally on trees and rocks in limestone country, in the form of rosettes 

 about 1 cm. across, which may be so closely crowded that the 

 rosettes are lost in a continuous intertangled mass of indefinite 

 area. Each branch divides into not more than 3 or 4 parts, no more 

 than 1 mm. wide, which may rise 2 or 3 mm. from the foothold. 

 The upper surface is ashy gray, tipped whitish, and with frequent 

 white or blackish hairs, not only along the margins, but sometimes 

 also on the upper surface. These are not different from the root- 

 like holdfasts on the white under surface. The tips slant upward 

 with toothed edges, or are puffed and blistered into lumpy swell- 

 ings, which l)urst outward, frequently leaving a thin, hood-like 

 structure. The form known as P. ascendens differs only in having 

 the tips dusted lightly with soredia. 



