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A\'hen the under surface is pure white or pale brownish, the lichen is 

 usually referred to its subspecies. P. Jiypotropa. 



Fruits frequent, as much as 2 cm. across, lifted on spurs some- 

 times 1 cm. high. They are cup-shape, flat or irregular, with a thin, 

 wavy rim. and in the center usually a torn hole. Spores undivided, 

 colorless. 9 to 14 by 6 to 8 microns. They sometimes appear 

 vaguely 2-celled. 



Pannelm perforata can be determined easily as the onlv Shield 

 Lichen with hairs on the margin and holes in the fruits. In fact, no 

 comparable Papery Lichen has this combination of characters. The 

 only other local Shield Lichen with marginal hairs is Cetraria 

 ciliaris, with much more finely divided lobes, and with blackish 

 granules scattered along the margin. The only other with perfo- 

 rated fruits is C. lacunosa, which has a net-like pattern of pits and 

 wrinkles seldom seen in P. perforata and no marginal hairs. 



But because P. perforata is variable, it has been divided un- 

 necessarily into several subspecies, which are here described briefly 

 to avoid confusion in case it is desired to study the group further. 

 All are alike distinct from other lichens, with ragged hairy margins 

 lifted high, and frequently, but not always, with central holes in 

 the fruits. For most purposes it is sufficient to name them all P. per- 

 forata, and if desired, to add these names as varieties, for they were 

 so listed by Tuckerman. 



Parmelia cetrata differs from P. perforata only in having lumps 

 of dusty soredia ranged along the margins. In this respect it 

 approaches P. perlata, from which it is distinguished by the mar- 

 ginal hairs and perforated fruits. 



Parmelia Jiypotropa has soredia like P. cetrata. but the under 

 surface is, at least in part, pure white or pale brown, blackening 

 toward the center. In this it approaches Cetraria lacunosa, but the 

 marginal hairs and soredia distinguish it. 



Pannelia crinita is densely covered with minute granules or 

 coral-like growths. The rare fruits are usually without any central 

 hole, and have soredia on the rims. Spores also are larger, 17 to 

 22 by 9 to 15 microns. This may perhaps deserve to rank as a dis- 

 tinct species, but as it is rare in the New York area, it ma}- more 

 conveniently be considered a subspecies or variety. 



(Group 7, the Leather Lichens, will include Sticta, Nephroma, 

 Solorina and Peltigera.) 



Ridge WOOD, X. J. 



