398 DR. LINDSAY ON WEST-GREENLAND LICHENS. 
convex instead of flat; and ultimately a black, irregular, verruezform, shapeless mass 
is the result. 
Various parasites, mostly hitherto considered Lichens*, have been described as occur- 
ring either on the apothecia or the thallus of S. saxicola, or on both, e. g. :— 
(1.) Conida clemens, Tul. (Kórb. Parerga, p. 458). On the apothecia. Sporidia 8, 
small, unequally oblong, 2-locular, hyaline. 
` (2.) Cercidospora Ulothii, Korb. (Par. p. 466). On thallus. Sporidia 4, fusiform or 
cymbiform, equally 2-locular, hyaline. | | 
(3.) Thelidium epipolytropum, Mudd (Brit. Lich. p. 298). On thallus. Sporidia 4-8, 
oblong or subfusiform, 2-locular, hyaline. | 
(4.) Lecidea episema, Nyl. (Prodr. p. 125). On thallus. Sporidia ellipsoid or oblong, 
and simple; or oblong, cylindrical, and 2-4-locular. 
(5.) Spheria Squamarie (Nyl. Scand. p. 133), already described under S. chrysoleuca. 
On thallus. I have given it the provisional specific name Squamarie, as it is desirable, if 
not necessary, for convenience in reference, that it should bear some short distinctive 
appellation. 
3. S.elegans, Link. J akobshavn, in fruit. Many forms or conditions oceur—some of 
them passing into PAyscia parietina, or undistinguishable from certain of its states. The 
colour of the thallus varies greatly with locality—from the brilliant vermilion of the type 
to the dull green of certain forms of parietina. It isa pale dirty green (e. g.) in shady 
places, on portions of the thallus shaded by stones, or on revoluted portions of the thallus. 
Sometimes the thallus is covered with sorediiferous spots, which become quite green under 
moisture. The cortical layer is frequently eroded in patches, as in P. parietina, exposing 
the white medullary tissue, and thus producing white-mottling of the thallus. This 
erosion sometimes involves large patches of the thallus. Potash struck a deep vermilion- 
red only in one specimen, while in many cases there was no reaction: thus there was 
none where the thallus was pale-green ; but in other cases there was every gradation of | 
colour-development between none and a distinct reaction. The apothecia exhibit similar 
changes of colour to those of the thallus. The disk, however, is sometimes deep vermilion 
where the thallus is very pale. Sometimes on a white (eroded) thallus the disk of the 
apothecia is black, the exciple thick and involute. The disk is also occasionally, in 
part or in whole, eroded similarly to the thallus, the hymenium being more or less 
destroyed.. The paraphyses are very beautiful and distinct microscopic objects, discrete, 
hyaline, with thick filaments, resembling the medullary tubes of many lichens. Hence 
S. elegans is one of the best lichens in which to study the structure of their paraphyses 
and their eonnexion with the tubular tissue constituting the medullary layer. They are 
distinetly articulated, the last two or three terminal cells being subspherical, frequently 
granular, or containing prominent nuclei. The terminal cells, or joints, which consti- 
tute the tips of the paraphyses, are much larger than the others; the seat of greenish 
* A detailed list of the Parasitic Micro-lichens, that affect species which occur in Greenland in common with other ` 
countries, will be found in my “ Enumeration of Micro-Lichens parasitic on other Lichens:" Quart. Journal of 
Microscopical Science, January, April, and October, 1869. 
