234 DR LAUDER LINDSAY ON THE SPERMOGONES AND PYCNIDES 
and convex, and dotted over abundantly with spermogones, like those of P. con- 
spersa. A morsel collected in FranKuin’s First Voyage, also in Herb. Hooker, is 
marked by NyLANDER as the true P. centrifuga ; it has neither apothecia nor sper- 
mogones, but the thallus is that of P. conspersa. 
Specimen 2.—Specimens from AcHarius, 1805, andfrom Mr Mour, Upsal, 
1803, in Herb. Hooker, Kew, Nyztanper also labels as the true centrifuga. 
They are quite the Norwegian plant collected by myself; and the apothecia and — 
spermogones alike are those of P. conspersa. A specimen from near Edinburgh, 
in Herb. Menzies, Royal Botanic Garden, Edinburgh, is a large-lobed form of 
P. conspersa, with spermogones sparingly distributed. 
Species 20. P. incurva, Fr., 
Which occurs in Europe and North America, appears to me to bear the same 
relation to P. conspersa that P. stygia does to P. Fahlunensis. The laciniz are 
narrow, convex—-sometimes sub-articulate and dotted over with spermogones, 
which are essentially those of P. conspersa. This plant is the Lichen incurvus, 
Ach.; Lichen multifidus, Dicks.; and P. recurva, Ach. 
Specimen 1.—Mr. Rozsson—from England, probably; Borrer, 1809—from 
Scotland, probably; and Dr. C. Lupwic, 1814, Riesengebirge; all in Herb. 
Hooker, Kew. In all cases the spermogones, as well as the thallus and apothecia, 
where the latter occur, seem to refer the plant to P. conspersa. 
Species 21. P. acetabulum, Dub., 
A native of Europe, Africa, and North America. It includes, I think, P. corru- 
gata, Ach., scarcely as a variety (Lichen corrugatus, Smith). In regard to the 
site and character of its spermogones, it closely resembles P. teliacea. They are 
scattered about the margins of the lobes as small black papillee, more or less 
obtuse or flattened on the summit. They are wholly immersed; in depth they 
extend through the whole thickness of the thallus; their form is oval, spherical, 
or irregular. The envelope is horny in consistence, and its structure resembles 
that of the cortical layer of the thallus; the ostiole is usually so minute as to be 
imperceptible. The spermatia are acicular—from {th to = th long, with a 
5000 8000 
breadth of about ;—,th. The sterigmata consist of 3 or 4 cylindrical or irregular 
articulations, and vary in length from =th to ;,,th. This species is comparatively 
abundant in certain continental countries—e.g. in France; and from the abundance 
and conspicuous character of its spermogones, it is a good species in which to 
examine these organs. WaLLROTH appears to have been familiar with its spermo- 
gones, which he described as his Spheeria epiblastematica. MAssALONGHO, accord- 
ing to Korper, has described—very erroneously, as it appears to me—the sper- 
matia of this species as globular or roundish. I have never seen them otherwise 
than straight and linear. 


