OF FILAMENTOUS, FRUTICULOSE, AND FOLIACEOUS LICHENS. 243 
irregular in form. The spermatia are rod-shaped, about anth long, and gath 
‘broad; the sterigmata consist of a few delicate, cylindrical articulations, and 
measure about ;th long only. 
SpPecIES 5. P. stellaris, Fr., 
A native of Europe, America, Africa, Asia, and Australia. There are several 
varieties, of which the most common and important is var. tenella, Schzerer, which 
is pro parte at least the Borrera tenella of the earlier authors. From the frequency 
with which the spermogones occur, and from their distinctness, —their colour being 
black or deep brown, while that of the thallus is gray or whitish—P. séellaris is 
one of the best species in which to study the spermogones of Physcia. Usually 
only the black, papillar ostioles are visible on the surface of the thallus, in the 
medullary tissue of which the body of the spermogone is immersed. Hence 
those black ostioles frequently resemble parasitic Sphwrice. The walls or envelope 
of the spermogone are at first gray, but subsequently become black. The diameter 
of the spermogone in the large-lobed form of the plant,— P. aipolia of authors,— 
is about y;th. The cavity is pluricellular and sinuous, as in P. ciliaris. 
Specimen 1.—On ash trees, Muirhall, Perth, W. L. L. ; associated with P. pul- 
verulenta, which it often very closely resembles. The spermogones and spores, 
however, especially the former, to a certain extent distinguish P. stellaris ; for the 
spores differ from those of P. pulverulenta chiefly in size. The spermogones of 
P. stellaris are always small, black or brown cones or papillze, with imperceptible 
ostioles ; while those of P. pulverulenta are largish ceesio-pruinose, thalline papillz 
or tubercles, opening by stellate-fissured ostioles. 
Specimen 2.—Kyles of Bute, on trees, 1852, W. L. L. This is a broad-lobed 
form. The spermogones are grouped in considerable numbers as small, puncti- 
form, immersed bodies. 
Specimen 3.—On ash trees, roadside, near Pitrodie, Carse of Gowrie, June 1856, 
W.L.L. The spermogones are smooth, prominent, black cones or warts, with 
imperceptible ostioles, scattered sparingly about the ends of the laciniz. Onash 
trees, roadside, near Glencarse, Carse of Gowrie,, May 1856, W. L. L. They vary 
greatly in size; but all are black, papillar, and distinct, the thallus being of a 
very pale grayish tint. In other narrow-lobed forms from the same locality, the 
spermogones are very prominent as brown, minute, round warts grouped on the 
convexities of the thallus. The spermatia are about gath long; the sterigmata 
are very delicate, composed of short roundish cellules or articulations. 
Specimen 4.—On trees, Glen Nevis, August 1856. Here the spermogones are 
mostly degenerate. They are, moreover, sparingly scattered, inconspicuous and 
small, being more mere black points than well-developed warts. Spermogones 
also abound in specimens collected on ash and other trees, at Annat Cottage, Carse 
of Gowrie, 1855, W. L. L. 
