212 Rhodora [NOVEMBER 
A KEY TO THE SPECIES AND PRINCIPAL VARIETIES OF 
CLADONIA OCCURRING IN NEW ENGLAND. - 
LiNcoLN Ware RIDDLE. 
ONE of the most urgent needs in the study of lichens at the present 
time is a set of keys to the larger genera. So far as I am aware no key 
to the New England species of Cladonia has ever been published. It 
is to contribute toward filling this need that the following key is here 
offered. It is based on the study of an extensive series of specimens, 
and has been tested by several students, both inexperienced and ex- 
perienced. Yet, in a genus where the species are as variable as in 
Cladonia and where such puzzling transitional forms occur, it is not to 
be expected that any key can be constructed that will serve for the 
determination of all specimens. It is hoped, however, that with 
material which is fairly typical, satisfactory results may be obtained. 
For the authors and synonymy of the species given, reference may be 
made to the check-list to be found on pages 215 and 216. 
Sect. I. Primary thallus persistent and crustaceous. Podetia short (mostly 
under 1 em.), club-shaped, simple or branched, apothecia pale brown, 
poorly developed. . . papillaria 
Sect. П. Primary thallus squamulose when present, often disappearing. 
Sub-Sect. l. Squamules when present medium-sized to small, whitish on 
under side. (For Sub-Sect. 2, see end of key). 
Series 1. othecia red. (Rarely the species of this series may have 
pale К<. эх brown apothecia, a condition known as var. ochro- 
car 
A. Podetia cylindrical, without cups. 
B. Green to yellow, smooth to warty, never sorediate. 
C. Simple below, sparingly Aoki cade above. 
D. Podetia reduced, squamules of thallus sorediate 
C. cristatella у. paludicola 
DD. Podetia well-developed, thallus not sorediate. 
E. Podetia with few squamules or none. ‚С. cristatella 
EE. Podetia densely squamulose..... C. cristatella v. vestita 
CC. Podetia branched throughout. ........ C. cristatella v. ramosa 
BB. Grayish, powdery-sorediate. 
C. Thallus scanty, podetia rarely squamulose. 
D. Podetia stout, sparingly branched, KOH + ...С. macilenta 
^ DD. Podetia slender, simple, KOH —.......... C. bacillaris 
CC. "Thallus well- developed, podetia short, squamulose, decorti- 
cate between the squamules.................. C. didyma 
AA. Podetia eup-bearing. 
B. Podetia medium-sized (mostly 2 em. or less). 
Podetia white-powdery-sorediate, cup with incurved margins, 
commonly proliferating. . . C. digitata 
CC. Podetia warty or granulate-sorediate, cups ‘dilated, rarely 
pronmrating........... eee lwp NP ERES c. coccifera 
