merit of discovery ? Certainly to the last observer. In the present 
instance the palm belongs to M. Crouan, unless the P. orbicularis 
of Kiitzing, described a short time previously, be a synonyme. 
My first acquaintance with this plant was at Roundstone, last 
summer, where, while dredging in Birturbui Bay, Mr. Mc’ Calla 
called my attention to specimens which came up abundantly in 
the dredge, attached to broken shells, stones, &c., and informed 
me that he had frequently observed the plant before. On exa- 
mination with the microscope, I at once recognized them as 
belonging to Peyssonelia, and not bemg then aware of M. 
Crouan’s memoir, I believed that I had alit upon an undescribed 
species, which I proposed to call P. dorealis. On communicating 
the supposed discovery to Mr. Thompson, he sent me a specimen 
dredged in Strangford Lough so long ago as 1833, and which 
had lain in his cabimet unnamed. And still more recently, on 
communicating with Mr. Berkeley, that learned Cryptogamist 
referred me to M. Crouan’s memoir, and favoured me with an 
authentic specimen of the French plant, which proves to be per- 
fectly similar to our Irish specimens. 
The genus Peyssonelia was founded by Decaisne, on the Fucus 
squammarius, Gm., a species common in the Mediterranean, of 
larger size, and more coriaceous texture than the present, and 
attached by a portion only of its lower surface. The Zonaria 
rubra, Grev.,in Linn. Trans. is probably the young of that spe- 
cies. I am only acquainted with Kiitzing’s P. orbicularis by the 
short description given in his work, by which it appears to be 
very closely allied to our P. Duby, but to differ in having its 
lower surface glabrous, and closely adherent. 
Fig. 1. PeyssoneLta Dubyi, growing on a dead shell of Cytherea lincta :—the 
natural size. 2. A vertical section of the frond, and of a wart. 3. Spores: 
—both magnified. 
