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4), Parmelia perforata and its near relatives (Group 6), all 

 larger, broad-lobed lichens except P. hispida {P. ascendens), 

 which does resemble P. comosa at first sight, but has tips swollen 

 into large, whitish blisters, bursting outward, while the fruits 

 grow on the upper surface of the lobes, not on the tips, and are 

 not bell-shaped. 



The hairs referred to must not be confused with the rather 

 similar growths which spring from the under surface of many 

 lichens, but which are root-like holdfasts. The hairs which in 

 those few species fringe the edges of stalks and lobes, do not 

 appear to be used for anchoring the lichen. 



Cetraria islandica. Iceland Moss. 



This is probably the most important of all lichens, long used 

 in northern countries both for fodder and for human food. 

 Though in the north it covers acres of otherwise barren ground, 

 only a few scattered colonies are known in the New York area, 

 on the Long Island coast, at the highest points of the Shawan- 

 gunks, and occasionally elsewhere, mostly at high altitudes. 

 Growing on the ground, Cetraria islandica (pronounced ice- 

 landica) forms tangled masses, usually about 5 cm. high, but 

 sometimes twice as large, of shining brown, strap-shaped stalks 

 and branches, commonly about 2 mm. but sometimes 1 cm. 

 wide. These curl, especially in drying, so that the upper surface 

 becomes a trough, the margins smooth or bordered with rather 

 uniform spines 0.1 mm. or so in length. While the upper surface 

 is not conspicuously different from the under, it is usually 

 darker brown, sometimes almost black, and more shining. The 

 under surface may show occasional wrinkles and channels, also 

 tiny pits or round patches of gray soredia less than 0.3 mm. 

 across. 



Fruits rarely found so far south, are borne on enlarged tips, 

 dark brown, oval or becoming irregular with age, up to 1 cm. 

 and more across, the rims toothed. Spores simple, colorless, 5 

 to 11 by 3 to 6 microns. 



So distinct is Cetraria islandica that no other ground lichen 

 could be mistaken for it, except perhaps C. hiascens, for no 

 other local upright species that grows on soil is shiny brown. 

 This color, with the spiny margins, should serve for complete 

 identification. 



