66 



the margin in such a way that some think they belong on the 

 under surface turned upward, as in Nephroma (Group 7), a dis- 

 tinction which, even if true, seems hardly to justify the new 

 genus Nephromopsis. Rims are toothed or warty. Spores undi- 

 vided, colorless, 5 to 7 by 4 to 5 microns. 



From the similar C. lacunosa, C. glauca and C. stenophylla, 

 C. ciliaris can be distinguished by the marginal hairs. It has also 

 a thinner substance, and more finely divided lobes. But these 

 four species must be compared carefully to avoid confusion, as 

 there are intermediate forms. C. lacunosa has the pitted surface 

 more pronounced, and its fruits often show a conspicuous hole 

 in the center. C. stenophylla has the lobes long and narrow. The 

 under surface of C. glauca quickly turns shining brown and then 

 black, its margins usually breaking into powdery white soredia 

 or coral-like growths. The hair-margined Parmelia perforata and 

 its relatives have much broader lobes which do not commonly 

 divide smaller than 5 mm. across, and do not regularly rise high 

 above the foothold. Other lichens with marginal hairs can be 

 eliminated by a glance at the illustrations. 



Cetraria lacunosa. Lettuce Lichen. 



Commonly seen with C. juniperina and C. ciliaris, or rather 

 more abundant than either on the highlands and in pine barren 

 swamps, where its larger tufts on bark and twigs look like 

 miniature lettuce. It may grow more than 10 cm. across, rising 

 2 or 3 cm. from the foothold. Lobes are often as broad as high, 

 but with the margins usually more or less divided and crinkled. 

 The net-like pattern of wrinkles with pits between is more 

 pronounced than in any other species of this group. The sub- 

 stance is rather thick and stiff, like thick paper. The margins 

 and often large areas of the surface are usually dotted with con- 

 spicuous black granules. The color varies from greenish gray to 

 rather dark green or brownish (greener when wet, as in most 

 lichens), while the under surface is characteristically white, but 

 sometimes turning brown or jet black on the older parts. There 

 are few or no visible holdfasts. 



Brown fruits up to 1 cm. across, of round, oval or irregular 

 shape, grow frequently close to the margins, but these clearly 

 spring from the upper, not the under surface, and are some- 

 times seen on short stalks 2 or 3 mm. from the margin. Large 



