OF FILAMENTOUS, FRUTICULOSE, AND FOLIACEOUS LICHENS. 239 
Specimen 1.—ScH @RER exs. 547; on the trunks of trees; Switzerland. Sper- 
mogones are abundantly studded over the margins of the lobes; they are black 
_or deep-brown punctiform or papillzeform bodies—in the latter case, flattened or 
‘depressed on the apex. The envelope is of a pale-brown cellular tissue. The 
spermatia are about ,1.th long; the sterigmata, —th to th long. Associated 
with the ordinary or spermatiferous sterigmata, occur numerous long, branching, 
delicate filaments, projecting into and occupying the cavity of the spermogone, 
as in P. physodes, P. saxatilis, &c. ; they have a breadth of about ;7;th to 7th. 
Specimen 2.—(Sub P. corrugata, Ach.) ; no habitat given; in Herb. Hooker, 
Kew. <Apothecia are large and plentiful. The spermogones are also plentiful 
about the margin of the lobes, as brown punctiform bodies, closely aggregated, 
sometimes sub-confluent—frequently surrounded by a brown ring, or eat in 
the centre of a roundish macula. The spermatia are about =,th long, and th 
broad ; the sterigmata are about ,,th long. 

25, “amit 
Species 22. P. Hottentotta, Ach., 
As its name would imply, an African species (syn. P. reticulata, Nees; Sticta 
Hottentotta, Ach.; Omphalodes Hottentotta, Flot.) The spermogones are frequently 
very large and distinct, crowded about the periphery of the thallus. NyYLANDER 
refers this plant to the P. acetabulum group; but the general aspect of the plant, 
as well as its apothecia and spermogones, would lead me to place it under 
_ P. saxatilis. 
Speciinen 1.—Cape of Good Hope; in Herb. Hooker, Kew. The spermogones, 
| in site, external characters and internal structure, are those of P. saxatilis. The 
_ spermatia are acicular, about th long, and ;4,th broad. The sterigmata are 
about ,{,th long, and consist of a few delicate linear articulations. 
SPECIES 23. P. olivacea, Ach., 
_ Which is found in Europe, Africa, America, Asia, and Australia. 
Specimen 1.—Var. exasperata, Ach. (syn. Imbricaria aspera, Mass. Korb. 
| 78.); on birch and other trees, foot of Morchone, Braemar, August 1856, W. L. L. 
| Almost the whole surface of the thallus is isidiiferous, or covered over with very 
minute cone-shaped or columnar warts—as occurs in P. sazvatilis or Evernia fur- 
| furacea. This form of P. olivacea bears the same relation to the type that the 
| var. furfuracea of P. saxatilis does to its type. It is an unnecessary refinement to 
| constitute this into a distinct variety, and still more into a distinct species. The 
| spermogones must be looked for on the smooth ends of the peripheral lacinize. So 
| difficultly recognizable are they, that it will be necessary to moisten the thallus 
| before they can be seen even under the lens. They will then become apparent, 
|, as extremely minute black immersed points. They cannot be confounded with 
| the isidioid warts of the thallus, which contain only gonidia and white medullary 
