10 



face is more or less covered with a fine down or nap and has usually 

 a few small, scattered holdfasts. In most of the species, the algal 

 cells are Nostoc, which should be in long chains, but which are 

 here imperfectly developed, and can be distinguished from the more 

 common Protococcus by their much smaller size, dull blue-green 

 color (contrasting with the bright green of Protococcus), and their 

 frequent appearance in chains of 3 or 4 together, sometimes more. 



Sticta amplissima. Spreading Leather Lichen 



Also called Lobaria amplissima. Found only occasionally on 

 tree-bark, more rarely on rocks, throughout the New York area, 

 but often large and striking, sometimes in mats 30 or 40 cm. across. 

 The rather flat branches and lobes wavy-margined, as much as 

 1 cm. across, but usually dividing into narrower tips. The upper 

 surface, smooth, or with narrow wrinkles, is usually pinkish gray 

 or pearl-gray when dry, but when wet is deep grass-green. The 

 downy under surface, pale bufif at the margin, may become umber- 

 brown toward the center. The algal cells are said to be Protococcus, 

 but look like Nostoc except that they do not occur in chains. 



Fruits are frequent and plentiful, light red when young, be- 

 coming brown or blackish with age. They are saucer-shape, up to 

 3 mm. diameter, usually rather regular, with a thin, smooth, pale 

 rim, and are scattered over the central parts ; but small, immature 

 ones appear near the tips as hemispherical warts 1 mm. or less in 

 diameter, each showing a depressed red dot in the center. Spores 

 4-celled, colorless, 30 to 65 b}' 4 to 8 microns. 



Sticta amplissima at first glance resembles the smaller Parmelia 

 tiliacea, and though usually tinted pinkish, may be greenish or bluish 

 gray. The distinct red color of the young fruits distinguishes it 

 from all Shield Lichens, and wetting it brings at once the char- 

 acteristic deep green color, much greener than any large Papery 

 Lichen which could be mistaken for it. Peltigera aphthosa which 

 also turns green when wet, has thickened and darkened veins be- 

 neath. From the other Leather Lichens, except S. herhacea which 

 is exactly like it in nearly everything but size, and vS". scrohiculata, 

 which bears warty soredia along the margins, 6^. amplissima stands 

 out by its resemblance to a typical Parmelia. It is also the only 

 Sticta which can be expected to fruit much in the New York area. 



