OF FILAMENTOUS, FRUTICULOSE, AND FOLIACEOUS LICHENS. AW 
nor spermogones. These Pycnides are quite superficial, removeable by the slightest 
touch; they are minute black perithecia, resembling, on the one hand, the peri- 
thecia of many Spherie, and, on the other, the spermogones of many Verrucaric 
and Graphideew. They are probably referrible to some Fungus, whose primary 
fruit does not occur in the specimens examined by me. The stylospores are plenti- 
ful, ellipsoid, pale-yellow, simple, about goth long, and gath broad. The sterig- 
mata are very short, linear and simple. The envelope is of a deep brown. Both 
plants are altogether anomalous in their characters; and until I have further oppor- 
tunities of examining them, I do not know where most appropriately to place them. 
GENUS IV. LeEptoeium, Fr. 
As a general rule, in regard to site, external appearance, and internal struc- 
ture or contents, the spermogones of this genus are precisely those of Collema. 
Nor am | aware of any very valid reason for dissociating Leptogiwm from Collema, 
as is done by NyLANDER and other modern authors. From the thallus in Lepto- 
gium being frequently more delicate and diaphanous than in Collema, and often of a 
beautiful pale-blue, or bluish-green colour, it is generally easier to see and examine 
the spermogones in the former than in the latter genus. This is especially the 
case in Leptogiwm tremelloides and its congeners, which possess the most beautiful 
and easily studied spermogones in the whole family of the Collemata. The sper- 
mogones of Leptogiwm are always immersed, flattened disks, resembling double 
convex lenses, of a pale brownish-yellow colour, with a central, round, very minute, 
brownish ostiole. The ostiole, though usually in the mature and young state of 
the spermogone punctiform, becomes comparatively large and patent in Z. satur- 
ninum, in which it sometimes gives to the spermogone the aspect of a young 
apothecium. The spermogones of Leptogiwm are more frequently seated on the 
flat surface of the lobes, near their margin, less often seated on the margins them- 
selves, than in Collema. In L. subtile, they are marginal, giving a denticulate 
character to the edges of the lobes, as in many Collemas. In L. fragile and L. 
phyllocarpum, they occur both on the margins and on the flat surfaces of the lobes, 
near their margins. Some forms of the beautiful LZ. tremelloides have distinctly 
denticulate lobes, from the presence of marginal spermogones, though generally, 
in this species, these organs are scattered over the flat surface of the lobes, near 
their periphery or margins. In L. tremelloides, the marginal spermogones are 
sometimes distinct largish cones, with a brown apical ostiole. The plant then 
resembles somewhat variety denticulata of Parmelia perforata. In this form of 
L. tremelloides, the body of the spermogone sometimes falls out in age, leaving 
small cup-like cavities, which give to the margin of the thallus a notched and 
very irregular character. The spermatia and sterigmata in Leptogiwm are precisely 
_ those described as belonging to Collema. 
VOL. XXII. PART I. | 4B 
