Descr. oot consisting of branching fibres, matted together. Fronds tufted 
2—12 inches long, exceedingly branched, and bushy, compressed or nearly 
flat, two-edged, narrow, linear, irregularly divided; main stems from half a 
line to nearly a line in breadth, alternating or subdichotomously branched ; 
branches distichous, frequent, often secund, patent, bearing one or more 
sets of similar lesser branches. Ramzi subulate, acute, patent, frmging the 
edges of the branches, secund, three or four at one side, and then three or 
four at the other; the lowest in position of each set simple, rarely crenulate 
along its outer edge, the rest pectinate along their inner edge with subulate 
teeth, which, in luxuriant specimens, bear a second or third series. Tudber- 
cles solitary, sessile on the edges of the stem and branches. Stichidia \an- 
ceolate or dichotomous, scattered along the edges of the upper branches, 
occasionally tufted, contaiming several oblong ¢etraspores, each marked by 
three pellucid transverse lines or zones, and finally separating into four 
granules. Colowr a fine transparent red, between crimson and scarlet. 
Substance cartilagineo-membranaceous, adhering, but not very closely, to 
paper. 
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A well-known, abundant, and beautiful species, and an especial 
favourite with amateur weed-collectors, and manufacturers of 
sea-weed pictures. It is also a very widely dispersed plant, 
being found im greater or less abundance and luxuriance, but 
with the same essential characters, in all waters from the North 
Cape to Cape Horn, m which last mentioned locality Dr. Hooker 
gathered specimens, im every respect identical with our most 
strongly growing British individuals. 
With the exception of this pelagic species, the genus Ploca- 
mium, 1 Which I include the Zhamnophora of Agardh, and the 
Thamnocarpus of Kiitzing (not of Harv. m Hook. Ic. Plant.) is 
confined to the Southern Ocean, where many very distinct species 
are found, some of which are of large size, having brilliant crim- 
son or rose-red fronds from a quarter to half an inch in breadth, 
and elegantly pectinato-pinnate. To all, the alternate, or secund, 
acute ramuli are common ; the only variation bemg that m some 
they are deltoid, in others subulate, and in some secund 7 pairs, 
in others (as in our P. coccineum) secund in fours. In one re- 
markable one, P. Hookeri, Harv., a native of Kerguelen’s Land, 
the branches bear, in addition to the subulate ramuli, occasional 
expanded, leaf-like processes. 
Fig. 1. PLocamiumM coccinEuM :—natural size. 2. Portion of a branch. 
3. Branchlet with a tubercle. 4. Tubercle. 5. Spores from the same, 
6. Branchlet with stichidia. 7. A stichidium. 8. Tetraspores, transversely 
parted. . 
