LEPTOGIUM. 161 



6), decelerate, ~ mic. Collema, Ack. Syn. p. 321. Lepto- 

 gium, Nyl. Syn. 1, p. 123. Collema corticola, Tayl. in Hook. 

 Journ. Sot. 1847, p. 195. Leptogium cimiciodorum, Mass. Mem, 

 p. 86. 



Trunks and rocks. From Canada and New England through- 

 ' out the northern and middle States (Muhleriberg), Acharius Syn. 

 1814. Ohio, Lea. Illinois, Hall. Mountains of Carolina & 

 Georgia, Eavenel. Alabama, Peters. Texas, Wright. Oc- 

 curring also in New Granada, S. America, Lindig herb. ,2, n.15 j 

 as in southern Europe, Anzi Lich. Venet. n. 14, etc. 



16. L. Tremelloides (L. fil.) Fr.; thallus middling to ample r 

 and large, loosely aggregated, round-lobed; lead-coloured; the 

 smooth and very entire lobes becoming crisped and complicate, 

 and beset, more or less, all over, at length densely, with con- 

 colorous, finally isidioid granules, passing now into minute 

 lobules ; apothecia middling-sized, lecanorine ; from flat becom- 

 ing convex, and excluding the thin, thalline margin. Spores 

 ovoid- ellipsoid, sub-muriform (the transverse series of spore- 

 cells oftener 4), decolorate, ^J mic. Tuckerm. Gen. p. 97. 



Collema Tremelloides , C. azureum, & C. diaphanum, Ach. L. U.p. 

 654. Leptogium Tremelloides max. p., L. diaphanum, L. reticula- 

 tum, & L. foveolatum, Nyl. Syn. 1, p. 124. 



Kocks and trunks, in the northern and middle States, com- 

 mon, Muhlenberg Catal. 1818. Canada, Macoun. Ohio, Lea. 

 Carolina and Georgia, Eavenel. Florida (v. reticulatum), Aus- 

 tin. Alabama, Peters. Mississippi (v. azureum), Veatch. Louis- 

 iana (a, and also v. azureum & v. reticulatum), Hale. Texas, 

 Wright. New Mexico, Fendler. Widely diffused, and dis- 

 tinguished by many names. Our northern form is the common 

 European lichen (v. cyanescens, Ach. Collema cyanescens, 

 Schaer.), which differs from the last species as well by its origi- 

 nally smooth, as its less regular thallus : this is not confined to- 

 cooler regions, but occurs equally well-marked in Louisiana. It 

 is however in the tropics that the best developed conditions of 

 the lichen are found ; and these appear also in our southern 

 States, the f. azureum being distinguishable by its more regu- 

 larly rosulate habit of growth, and its perfectly smooth and 

 coerulescent thallus, which hi the scarcely otherwise differing 

 f. reticulatum, Mont., becomes regularly and at length very 

 deeply (foveolatum, Nyl.) lacunose -reticulate. There remains. 

 11 



