332 DR. LINDSAY ON WEST-GREENLAND LICHENS. 
green under moisture. Some of its forms apparently pass into Jahlunensis. In the 
hymenium a blue colour is indistinctly elicited under iodine. Sporidia simple, colour- 
less, oval or oval-oblong, 0006" long, and 00025" to 0003" broad. 
6. P. lanata, L.—Jakobshavn, on granite, sterile; Illartlek Glacier, in fruit. Thallus 
sometimes as brown as that of olivacea—or paler, a fine chestnut colour,—a variation in 
character that is important in connexion with the close interresemblances already referred 
to of forms of omphalodes, olivacea, arctica, Jahlunensis, and stygia. 
7. P. encausta, Sm.—Jakobshavn. Colour of thallus sometimes green, especially when 
moistened, or buff or brown. Young and pale (etiolated) states occur on the under, shaded 
and moist surfaces of rocks. These states give a greenish-yellow reaction with potash. 
In the specimens examined by me, the thallus is mostly white and decayed. It is studded 
over with a parasite in the form of minute, subspherical or very convex, crowded, black 
apothecia or perithecia, resembling the apothecia of Abrothallus Smithü. They exhibit, 
however, no structure. 
Gen. 14. Puyscra. 
1. P. pulverulenta, Schreb.—Jakobshavn. A few fragments only occur, sterile, of 
olive-green colour, some terricolous, others growing on the underside of Umbilicaria vellea. 
Th. Fries does not give pulverulenta as a Greenland lichen, though he describes muscigena, 
Ach., as fruiting and as common throughout the area of his * Lichenes Arctoi' (p. 63). 
In the Kew Herbarium I saw the ordinary form (the type) in fruit, with the thalline edges 
or periphery much eroded, labelled as from the * North Pole" (Parry*) ; and in that her- 
barium it appeared to be a very Arctic species. It passes into, and is apt to be con- 
founded with obscura and stellaris. Var. pityrea, Nyl., is just a white-pruinose form, in 
which the pruinosity is so abundant as to cover the whole thallus. Th. Fries (L. Spitsberg. 
p. 13) mentions another form with the thallus densely white-pruinose, giving it the facies 
of stellaris or cesia. In Europe Karschia pulverulenta, Anzi (Körb. Parerga, p. 460), 
is sometimes parasitie on the upper surface of the thallus. 
2. P. cesia, Hffm.—Kudlesæt: sterile, with a dark lead-coloured thallus. Jakobshavn, 
on granite and gneiss; microphylline, with both apothecia and spermogonia. The 
apothecia are wholly black and lecideoid, exciple and disk alike; flat and regularly - 
round in outline. The spermogonia are very minute black papillæ, conspicuous under 
the lens when the thallus is moistened. The laciniæ are sorediiferous, and of the usual 
lead-grey colour. Some macrophylline forms approach stellaris. In Scandinavia, the 
thallus of cæsia is the site of the parasitic Buellia convexa, Th. Fries (Arct. p. 234). 
3. P. stellaris, L.—Jakobshavn. Associated with Placodium elegans; a fragment 
merely, but bearing both apothecia and spermogonia. Disk of apothecia cesio-pruinose. 
Sporidia 2-locular, ellipsoid, brown or olive, straight or slightly curved, 00040” to 00060” 
long, and 00020” broad. The spermogonia are black papille; the sterigmata 0006" long, 
sometimes comparatively simple, or composed of few articulations. Spermatia straight 
rods 00015” long. Various microphylline, sterile forms of the plant sid both on the 
under and upper surfaces of the thallus of Umbilicaria vellea. . 
* Vide author's “ Lichen-Flora of Greenland,” Trans. Botan. Society of Edinburgh, vol. x. pp. 52 & 33. 
