DR. LINDSAY ON WEST-GREENLAND LICHENS. 321 
Gen. 9. CETRARIA. 
1. C. aculeata, Ehrh.—Jakobshavn. Always sterile. Sometimes corticolous ; on bark 
of birch (as are also Lecanora tartarea, var. Srigida, and Cetraria Islandica, var. leuco- 
meloides). Not mentioned by Th. Fries as a Greenland lichen at all. In the present col- 
lection, however, I met with various forms, which I cannot but refer to this type. Some 
states, exasperate with bristles, agree with French specimens (in Nylander's Exs.) of 
var. acanthella. Aculeata is not very rare in Spitzbergen, though only found sterile, 
says Th. Fries (L. Spitsb., p. 10); and it would be singular if it were not to occur also 
in Greenland. Fries has probably referred its puzzling Greenland forms to Alectoria 
divergens (= Thulensis, p. 29) or ochroleuca (e.g. var. nigricans), with which it is fre- 
quently associated and intermixed, and from which it scarcely differs sometimes save in 
colour. With forms of these Alectoria it is very apt, in certain conditions of growth, to 
be confounded. This being the case, it is a very artificial and arbitrary classification 
that separates aculeata from ochroleuca, placing it in a different genus. The old genus 
Cornicularia was much more natural and convenient than its modern substitutes: and 
anomalous as some of its species were, they were not more so than are those of many 
genera of the present day ; while it was better for the student's purposes to find them 
grouped together than scattered, as they now are, through various genera such as Par- 
melia (e. g. stygia, tristis, and lanata). Equally artificial is the separation of Platysma 
from Cetraria. Glauca is a Parmelioid form, and stands appropriately enough in a 
separate section (not genus); but cucullata and nivalis are too closely allied to Islandica 
to permit of such severation. 
2. C. Islandica, L.—Godhavn, Egedesminde, Lyngemarken, Jakobshavn, Illartlek 
Glacier. Various forms occur, always sterile; including crispa, and several states interme- 
diate between it and C. Délisei, C. nigricans, and C. odontella, as well as those so-called 
* species " themselves. It is generally terricolous ; but one form, with margins as fibril- 
lose as Physcia leucomela, and otherwise resembling that plant, occurs on twigs (pro- 
bably of birch) near Jakobshavn. This state, with laciniæ as long and flexuous as in 
P. leucomela, might appropriately bear the name (if name is required) of form or variety 
leucomeloides. The form from Lyngemarken is decayed, and as white as P. leucomela, 
with a black, Verrucarioid parasite, very conspicuous on these whitened laciniæ, resem- 
bling externally that which occurs on the young thallus or prothallus of Lecanora tar- 
tarea, var. frigida. 
The thallus of Islandica is sometimes of a beautiful vermilion colour, or is red-mot- 
tled, about the base (e. y. in Egedesminde specimens). None of its forms give any reac- 
tion with potash.  Fibrillosity of the margin of the laciniæ is sometimes a very marked 
character. The fibrille are sometimes very long, and are split at their ends into tufts of 
secondary fibrillulæ. The crispa forms are sometimes also very denticulate, with narrow 
laciniæ, closely tufted, and of a very deep glossy brown colour. = 
Some forms closely resemble, save in colour, C. cucullata. The laciniæ are broader, 
much curled *; the margins smooth, destitute of fibrillæ, cilia, or spermogonia ; the 
* In the Edinb. University Herb. what is called ©. Grenlandica by Despréaux, collected in Labrador in 1005, 
is this form of C. Islandica, with the thallus as much curled as in C. 
VOL. XXVII. 2x 
