— 92 — 



lighter at the centre and sometimes powdery. The margin is irregular, and 

 in the older specimens is torn. Below it is a sooty-brown or black, very^ 

 granulate and deep pitted, has no fibrils. The apothecia are small and clus- 

 tered in the spaces between the pustules, near the margin of the thallus. 

 This species is found on rocks throughout the Eastern and Southern states, 

 especially in the mountains. ' 



Umbilicaria pustulata (L.) Hoffm. Plate IX. 3. Thallus small to 

 medium, one-leaved, very papulous ; in color ashy becoming brown, lighter 

 at the centre and more or less powdery. In young specimens the margin is 

 entire and slightly waved, as the plant grows older the margin breaks and 

 appears ragged. The under surface is brown, growing lighter toward the 

 centre; is finely granulate with deep pits. The apothecia are small and 

 numerous, situated between the pustules of the thallus and toward the mar- 

 gin. The variety, papulosa, is so nearly like the specimens in appearance 

 and internal structure that many lichenists include it ^'x'Oa. pustulata. 



U. pustulata resembles U. Pennsylvanica very closely on the upper 

 surface, except that in the latter the pustules are more irregular in outline, 

 and are depressed at the centre. Beneath they are easily distinguished. 

 U. Pennsylvanica is a sooty-black and is much more granulate than U. 

 pustulata and the pits are not so marked. 



RADULA. 



By Wm. C. Barbour. 



(Contintied from page 47. May, 1902.) 



Key. 



I. Leaves closely imbricate (somewhat distant in R. tenax) 2, 



Leaves loosely imbricate 7. 



Leaves distant R. obconica. 



2, Stems dichotomously branching R, tenax. 



Stems more or less pinnately branching 3. 



3, Mouth of perianth entire or nearly so 4. 



Mouth of perianth emarginate or crenate 6. 



4, Perianth compressed, not noticeably narrowed at apex 5. 



Perianth subinfiated, narrowed at apex R. Hal lit. 



5, Perianth short, oblong-quadrate , R. Caloosiensis. 



Perianth long, obconic , R. complanata. 



6, Perianth compressed cylindric R. australis. 



Perianth funnel-form, mouth compressed R. Xalapensis. 



7. Leaves flaccid, rotund oval, subrepand-dentate R. Sullivantii. 



Leaves subascending or semivertical, broadly obovate, entire. 



R. Bolanderi. 



Radula tenax Lindb. {R. pallens Sulliv,) 



This species is found mostly in mountain regions, ranging from the 

 Catskills of New York to the mountains of North Carolina, It is dioicous, 

 with firm, rigid stems ; the leaves rather remote, slightly, if at all, decurrent, 



