199 



New York area, it is doubtful whether this form deserves to be 

 considered a subspecies or even a variety. 



Physcia grannlijera. Granular Blister Lichen 



Also called Anaptychia granulijera. A poorly defined species, 

 to be looked for in the New York area on tree-bark. Probably rare. 

 It resembles somewhat P. pulverulenta, but instead of brown is pale 

 gray or white, with whitish, mealy granules near the tips, also with 

 white masses of soredia and tiny prongs scattered over the upper 

 surface. The under surface is pale, with black root-like holdfasts. 

 Fruits are usually frosted white, with spores variously described. 



From pale forms of P. pulverulenta it can be distinguished by 

 examining a microscopic section, in which the upper surface con- 

 sists of parallel fungus threads (the characteristic structure of the 

 genus Anaptychia) instead of the cellular structure of Physcia 

 proper. This can perhaps be seen clearly by an expert microsco- 

 pist, but there is doubt whether the character follows natural 

 relationships, or whether it has resulted in some specimens being 

 placed with species to which they are not actually related. It is 

 probably in reality a minor variant. P. granulijera is mentioned 

 doubtfully here, as unlikely to occur, though it has been found 

 in Pennsylvania. 



Physcia caesia. Blue-Gray Blister Lichen 



Though named a hundred years ago, this species is not well 

 understood. It occurs on cliffs containing lime, also sometimes on 

 trees, resembling P. stellaris, though, in place of the central crust, 

 there is a mass of intertangled branches. The upper surface is 

 pale gray, the under surface also pale, sometimes darkening, while 

 the holdfasts are usually dark. The determining character is the 

 presence of compact, nearly hemispherical mounds of pale blue- 

 gray, or occasionally whitish, soredia as much as 5 mm. in diameter, 

 studded along the main branches, where fruits would be expected. 

 Care must be taken not to confuse these with the dots of w^hite pith 

 exposed where snails have eaten the fruits of P. stellaris. Soredia 

 are masses of powder which come off as whitish dust on the fingers 

 when handled, while the pith has the substance of white cardboard. 

 Fruits and spores, when present, are like P. stellaris. 



