
OF FILAMENTOUS, FRUTICULOSE, AND FOLIACEOUS LICHENS. 249 
tions. The cavity is divided into numerous sinuous compartments, as in He ciliaris 
and P. obscura. The length of the spermatia is usually about 7th to auth. 
Specimen 1.—On ash, Muirhall, Perth, W. L. L.; associated with P. stellaris, — 
with which it is frequently very apt to be confounded. In regard to-the differ- 
ential diagnosis of these two species, I may refer to what I have already said 
under P. stellaris. Old Scone Road, Perth, April 1855, W. L. L.; associated with 
P. obscura, with which, also, this species is apt to be confounded. The spermo- 
gones are very abundant as obscure, irregular cones or warts, of the same colour 
as the thallus ; the apex deeper brown; the ostiole seldom distinct when round, but 
more conspicuous when stellate-fissured. They are generally grouped, sometimes 
confiluent—two or three spermogones uniting to constitute one spermogonal wart. 
They are thusvery different from the spermogones of P. stellaris ; which spermogones 
serve to distinguish—where other marks fail—P. pulverulenta from P. stellarcs. 
| Specimen 2.—On trees, Glen Nevis, August 1856, W. L. L.; associated here, 
also, with P. stel/aris, and sometimes scarcely distinguishable therefrom. The sper- 
mogones are brown, sub-confluent, or closely grouped prominent tubercles, seated 
on the convexities, and about the extremities, of the laciniz. The spermatia are 
| about auth long; the sterigmata are very delicate and irregular, consisting of 
shortish articulations. 
Specimen 3.—Carrigaloe, Cork Harbour; coll. Carrott. The spermogones 
| are pale-brown, largish, white-pruinose papille, opening by stellate-fissured 
| ostioles. The spermatia are ;;th long, and s,0th broad. Ona wall, Sidlaw Hills, 
| 1844, GarpINER; in Herb. Hooker, Kew; a good typical specimen. The spermo- 
| gones and spermatia are as just described. 
| Specimen 4.—ScH2RER exs. 356 (sub a. allochroa, a. corticola) ; on the trunks and 
| branches of trees about Belp. The spermogones are pale-brown, indistinct papillee. 
_ slightly pr ominent, semi-immersed. The spermatia are about mth long, and very 
| abundant ; the sterigmata are very irregularly articulated. 
Species 11. P. muscigena, Ach., 
Which occurs in Europe and North America, seems to me only a muscicolous 
| form of the preceding. The spores are of the same form and size as in P. pulveru- 
| lenia; the spermogones have the same structure, though they are usually smaller 
| papillee, of a darker brown colour—naked, or not so frequently pruinose. 
| Specimen 1.—Guldbrandsdal, Norway, SomMERFELDT, Un. Itin. 1828; also 
| Switzerland; in Herb. Hooker, Kew. Both apothecia and spermogones occur. I 
| have gathered this plant abundantly at various points on the Dovrefjeldt range 
of mountains in Norway. 
Species 12. P. aquila, Fr. 
Specimen 1.—LeEicuton exs. 144 (E. B. 982; Move. and Nzst. 1049) ; Torquay, 
| Devonshire. The spermogones closely resemble those of Parmelia stygia; they 
| are plentiful as small brown tubercles, occurring about the ends of the laciniz. 
| VOL, XXII. PART I. ae 
