60 



opposite along the stalks, though in some specimens this is 

 hardly noticeable. Stalks and branches are of fairly uniform 

 width, up to 2 mm., and the blunt tips are commonly bare of 

 hairs. 



Fruits, exceedingly rare in the north, on tips of branches, 

 gray, with a whitish bloom, or nearly white, as much as 6 mm. 

 across, with a ragged rim. The spores have a blackish tint char- 

 acteristic of Physcia, and are plainly divided into two cells. 

 Size 35 to 55 by 16 to 25 microns. 



Most Physcias are stalkless Papery Lichens (Group 8), all 

 easily separated from similar forms by the blackish, two-celled 

 spores. They differ from Parmelia and Cetraria in the color of 

 their fruits, which is never chestnut brown, but usually slate- 

 gray or blackish, with a gray or white bloom, and dull rather 

 than shining. In cases such as Physcia leucomela, where fruits 

 are not expected, the shape and color of the lichen must de- 

 termine it, and in this case they are sufficient. 



Physcia ciliaris. Fringed Lichen. 



Also called Anaptychia ciliaris. Much like P. leucomela, but 

 found only north of the New York area. It differs in growing 

 on rocks or soil rather than tree-bark, in its usually darker color, 

 and in a tendency of the hairs to remain pale instead of blacken- 

 ing. As it is hardly ever found south of Canada, there is no need 

 of describing it in detail. 



Physcia comosa. Bell Lichen. 



Also called Anaphtychia comosa. Another species rarely seen, 

 but to be looked for on tree-bark. It is pale greenish gray. 

 Though its stalks will seldom exceed 2 cm. in length, they 

 broaden to as much as 2 mm. at the forks, and the hairs which 

 border them are usually short and inconspicuous. The stalks, 

 branches and tips look somewhat swollen, as do many Physcias 

 (Blister Lichens). The most distinctive character is the bell- 

 shaped fruit, unique among local lichens. The stalk behind the 

 fruit has a globular swelling, while the papery rim distends like 

 the mouth of a bell. 



Only a few lichens have hairs along the margins of stalks 

 or lobes. Beside the Physcia species just described, the chief of 

 these are: Physcia hispida (Group 8), Cetraria ciliaris (Group 



