DR. LINDSAY ON WEST-GREENLAND LICHENS. 323 
forms resemble the spermogonia in some states of Islandica; and this is an additional 
reason for not dissociating nivalis and cucullata from Islandica in a separate genus. 
Potash develops no reaction on the cortical, nor iodine on the white medullary, tissue. 
The natural colour of nivalis, as in cucullata, is a beautiful lemon-yellow ; but it is 
seldom so brilliant or pure as in the handsomer Norwegian plant. Passage-forms into 
cucullata lose their lacunosity ; while the tips of the laciniæ become rounded. Wher- 
ever both liehens occur in the same district or country, they are generally intermixed, 
and are apt to be confounded. Hence, in the Kew Herbarium (e. y. some Swiss speci- 
mens) and all large herbaria, forms of the one are commonly mistaken for conditions of 
the other. 
Genus 10. DACTYLINA. 
l. D. arctica, Br.—On a dry mossy slope, near the Illartlek Glacier, in considerable 
abundance. I did not see the specimens in this collection, which Brown says (Trans. 
Botan. Society of Edinb., vol. ix. 1868, p. 453) were “ accidentally packed in the Fungi 
parcels." Specimens in my herbarium from the Kikerton Islands * (Taylor) sent me by 
Prof. Dickie have the characters partly of Dufourea madreporiformis (Scher. Exs. 85) :—of 
Dactylina arctica, var. madreporiformis, Ach.; of Thamnolia vermicularis, var. subulifor- 
mis (Scheer. Exs. 86); and of Dactylina ramulosa, Hook., a plant of Arctic America, the 
Rocky Mountains, and Behring's Straits. Dufourea muricata, Laur., which I have not 
seen, is probably a transition-form between arctica and madreporiformis. Ihave no hesi- 
tation in referring arctica, madreporiformis, and ramulosa to one genus, and, indeed, to 
a single species, discarding the genus Dufourea as unnecessary. What Dickie labels 
Dufourea madreporiformis is Dactylina arctica, sterile, but quite agreeing with speci- 
mons of arctica in my Herbarium from Arctic America (Great Bear Lake, Richardson). 
The Kikerton form of arctica bears both apothecia + and spermogonia in abundance. 
The thallus is quite as ramose as madreporiformis, whose branches, however, are nar- 
rower in general. It is very different from that of the usual sterile forms of arctica in 
my herbarium, from Arctic America and Cape Adair, which exhibit simple, ventricose, 
finger-and-thumb-like offshoots from a general, horizontal, hollow, podetium-like thallus, 
frequently 1" long and nearly 1" broad. In the latter case, hollowness is visible by 
reason of the greater size or dilatation of the podetia and their offsets. Madreporifor- 
mis of equal size would be equally hollow. In the latter species (if a species) the podetia 
are sometimes hollow, though generally filled with a spongy, white medulla, which 
gives no reaction with iodine. Nor does the cortical layer show any colour-change 
* Tn Arctic plant-collections, I find three places of similar name, that are apt to be confounded, if they .are different 
localities, viz. :— 
l. Kikerton, or Kikkerton Islands, which Mr. Brown tells me are in Cumberland Sound, near Frobisher's Straits, 
and are therefore unconnected with Greenland. 
2. Kikertait (=“ The place of Islands”) mentioned by Hayes, in his ‘Open Polar Sea’ (London, 1867, p. 68). 
3. Kikertak, in Greenland (teste Th. Fries, * L. Arctoi”). 
t It is noteworthy that, though apparently abundant in Greenland, D. arctica is always there sterile —according 
to Fries (Arct. p. 160). 
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