DR. LINDSAY ON WEST-GREENLAND LICHENS. 339 
colouring-matter ; generally subovate or subpyriform. They are more granular, and more 
frequently contain nuclei than the other articulations. Henee, when detached, they 
have the aspect of many sporidia or stylospores. Their colouring-matter is sometimes 
distinctly limited, e. y. to the terminal cellule, or to a portion only thereof*. The sporidia 
are very variable in size and form, hyaline, very delicate, generally oval, sometimes 
slightly curved, sometimes simple; or polari-bilocular and physcioid; or equally 2-locular, 
with a median. septum, and with (or without) a central constriction, giving a figure-8 
character ; about :00040^ long and :00020” broad. 
The thallus, as well as the apothecia (disk and exciple alike) are the seat of a parasite, 
which occurs in the form of scattered or crowded, sometimes confluent, black papillæ, 
containing sporidia, that are about :00020" long and :00009" broad, oblong-ellipsoid, 
2-locular, brown in maturity, olive in the young state. These sporidia are very different 
from those of the Squamaria, and cannot be confounded therewith. Nor can the parasite 
be mistaken for the spermogonia of S. elegans, which are described and figured in my 
* Mem. Spermog.’ (p. 300, plate xv. figs. 27-29). The Greenland parasite has the cha- 
racters of some species of the genus Ticothecium, Fw., emend., as they are described by 
Körber (in his * Parerga,' p. 467). But none of the said species are represented as in- 
festing the apothecia of the Lichens on which they occur. 
In the Kew Herbarium several specimens of $. elegans occur from Greenland and dif- 
ferent parts of the Arctic regions (e.g. Igloolik, Sir Edward Parry), all of them saxi- 
colous, and in fruit. In Spitzbergen, they sometimes occupy unusual habitats, e. y. 
the old weathered horns of Reindeer (Th. Fries, * L. Spitsberg.’ p. 14). 
In some districts of Greenland, S. elegans would appear to occur in such abundance 
as to give a character to the rock-scenery. Thus Hayes, speaking of Port Foulke, says 
that the rocks are almost everywhere covered with a lichen of an orange-red colour, 
growing in “immense patches,” imparting “ a cheerful hue to the rocks ;” while “ Tripe 
de roche,” which was still more plentiful, gave them, on the other hand, “a mournful 
look” (‘Open Polar Sea,’ p. 398) +. 
I see no good ground for separating Placodium and Squamaria as genera. On the con- 
trary, it would be much more convenient, and quite as scientific, to arrange in a single 
group all the Lichens, having a subfoliaceous thallus intermediate between Parmelia 
or Physcia and Lecanora, with sections founded perhaps on the character of the 
thallus, on the one hand, or of the sporidia, on the other. The character of the sporidia, 
however, is unsafe even for the establishment of sections, inasmuch as there are (e. g. 
among the Lecanore and Lecideæ) many Lichens whose sporidia are, at different stages 
or in different states of growth, both simple and compound. This difficulty meets the 
student in connexion with the numerous subgenera into which Continental lichenolo- 
gists have divided the heterogeneous genera Lecanora, Lecidea, and Verrucaria. 
Genus 18. LECANORA. A 
The subdivision of this great genus into the numerous genera quoted by Th. Fries (e. g. 
* This limitation is even more distinct in Lecidea Grenlandica (q. v.). 1 
t Compare remarks on the physiognomy of the Greenland Lichen-flora in my paper on “the Lichen-Flora of 
Greenland" (pp. 36-39 & 65). 29 
Z 
