31 



and those who wish may call the above-described forms by their 

 names as separate species. 



Usnea tricJwdea Ach. Hair Lichen 



Differs from all other Usneas in its extreme slenderness, 

 the main stalk often only 0.2 mm. thick, and tapering to hair- 

 like tips. Not so common as the others northward, it is fairly 

 abundant in the pine barrens. Typically very pale green or soft 

 greenish gray. The fruits, usually along the stem, but rare, 

 average smaller, not over 4 mm. diameter, round and smooth, 

 of the same color as the stems, and wdth few or no fibrils on the 

 rim. The fibrils of the branches also may be widely scattered. 

 Though distinct in its slenderness, U. trichodea has forms which 

 approach U. barhata, and may be called by either name. 



Spores of the different species of Usnea do not differ materi- 

 ally from each other. All are ellipsoid, colorless, undivided, 

 about 6 to 10 by 4 to 8 microns, and come 8 in each sack. They 

 may usefully be studied under the compound microscope to 

 distinguish Usnea from possible confusion with Ramalina and 

 Teloschistes, which have 2-celled spores. 



The conspicuous character by which Usnea may be dis- 

 tinguished from other lichens in Group 3, is the presence of 

 fibrils and branchlets standing at right angles to the stalks 

 and branches, and fringing the fruit-rims. Ramalina and Ever- 

 nia (Group 4), beside lacking the Usnea fibrils, have their 

 stalks variously flattened, angled and channeled. 



Alectoria, the only other lichen easily confused with Usnea, 

 usually turns brown in contrast to Usnea's greenish gray, and 

 through Alectoria bears fibrils, these do not usually occur along 

 the main branches. While the surface of Usnea tends to be dull, 

 that of Alectoria becomes polished and shining. In the New York 

 area, Alectoria is usually more slender than any Usnea except 

 U. trichodea. For a decisive test, however, pull a stalk until it 

 breaks. Usnea is constructed like a telephone wire, with a tough, 

 hard, pure white core, surrounded by more brittle "insulation," 

 Alectoria more like a garden hose, either hollow, or partly 

 stuffed with weak threads. 



Along the southern coast, beginners may confuse the hang- 

 ing Usneas wdth the so-called moss w^hich everywhere droops 

 from the trees, but which is neither a moss nor a lichen. It is 



