Having, in the ‘British Flora’, committed the error of des- 
cribing a variety of C. thuyoideum under the name C. tripinnatum, 
an error unfortunately continued im Wyatt’s admirable ‘ Algze 
Danmonienses’’, I have peculiar satisfaction in affording to the — 
British botanist a figure of the ¢rve plant, of which I am the 
more certain, having compared our Irish specimens with one 
communicated to me from the Mediterranean, by my friend 
Professor J. Agardh. Notwithstanding some slight differences, 
I cannot but regard the Inish plant as belonging to the same 
species as that from Cette. The latter is more luxuriant, rather 
more robust, and has the ultimate ramuli rather longer, and 
perhaps it is more irregularly branched than ours. But the 
main character,—that by which the species is chiefly distin- 
guished,—of having a minute ramulus on the first jomt of the 
pinne, is common to both. 
Though the habit of C. tripinnatum is very like that of C. gra- 
cillimum, it will be perceived that its microscopic characters have 
a greater resemblance to those of C. Borreri, from which the 
axillary ramulus, and the distichous growth chiefly separate it. 
Mr. Mc’ Calla has, as yet, found very few specimens, and these 
accompanied C. thuyoideum, growing on the perpendicular sides of 
steep rocks at the extreme limit of low water. No other British 
station has yet been observed, but it can hardly be doubted that 
it will yet be added to the Flora of Devonshire or Cornwall. 
Grateloup’s specimens were probably collected on the opposite 
shores of the channel. 
Fig. 1. CALLITHAMNION TRIPINNATUM :—the natural size. 2. A plumule or 
pinnated-branch. 3. One of the smaller pinne. 4. A pinnule, with 
tetraspores :—all more or less highly magnified. 
