Se ee SP aS eee ee ee Se ee | A ee ae Tee i 
1910] RIDDLE—STEREOCAULON 287 
is correct, AcHarrtus should be cited as having definitely estab- 
lished the genus Stereocaulon in Methodus Lichenum (1803), p. 314, 
with Lichen ramulosus Swartz as the type species. It is true that 
the name had been used by three previous authors, but none of 
these can be held to have established the genus, according to present 
ideas. SCHREBER first published the name with a brief diagnosis 
in LinNaEvs’ Genera Plantarum, ed. 8 (1791), p. 768, but no species 
is cited under the genus. SCHRADER, in Spicilegium Florae Ger- 
manicae (1794), p. 113, used the name with a single species, S. 
corallinum, a species based, however, on an imperfect lichen which 
later proved to be a Pertusaria. Finally, Horrman, in Deutsch- 
lands Flora, II (1795), p. 128, gives a genus Stereocaulon, with nine 
species; of these nine only three are now recognized as belonging 
to the genus, the others included two species of Sphaerophoron, 
one Collema, one Lichina, and two imperfect forms; HoFFrMAN’s 
genus, therefore, “embraced elements altogether incoherent” and 
hence cannot be considered valid. AcHARIUs thus remains the 
first author to place the genus on a solid foundation. The generic 
characters may be stated as follows: 
Thallus of two parts, a primary horizontal thallus, which in most cases 
Soon disappears, and erect, solid, cylindrical, ecorticate podetia; thallus of 
minute, rounded or irregularly flattened squamules, which are typically gray, 
sometimes creamy or white, and which also cover the podetia more or less 
thickly; apothecia lecideine; spores fusiform to acicular, hyaline, plurilocular. 
—Closely related to Cladonia, from which it differs in the solid podetia and the 
plurilocular spores, the latter character also serving to,distinguish this genus 
from Pilophorus. 
The term “‘squamules”’ (used by ACHARIUS, E. Frtes, SCHAERER, 
and others) is here adopted, in preference to the term ‘phyl- 
locladia” (used by Tu. Fries and by TucKERMAN), for the thalline 
outgrowths which constitute the thallus of species of the § Pro- 
STEREOCAULON, and which occur so characteristically on the podetia 
ofall species. The term is in current use for such thalfine structures 
in other genera of lichens, and especially in the genus Cladonia, 
with which the squamules of Stereocaulon are strictly homologous, 
although somewhat modified. 
In the descriptions of the species I have made no attempt to 
_ describe all the details of the plant, many of them unimportant, 
