segments, often beautifully fringed; and the truncate tips finely cut. Tu- 
bercles abundant, as large as poppy-seed, scattered along the margin of the 
frond, both of the smaller and larger divisions. Tetraspores crowded in the 
ultimate ramuli, on plants more slenderly branched than those that bear 
tubercles. Colour a brilliant crimson-lake, becoming brighter in fresh water, 
and at length discharged on long steeping. Substance membranaceous, soft, 
adhering to paper in drying. 
One of the rarest of the British Algze, almost confined with 
us to the northern shores of Scotland, and the Orkney and 
Shetland Islands, and m no place found im abundance. In . 
general British specimens are small, rarely attaining the size 
of that represented im our plate, which is copied from the 
largest of those presented to us by Messrs. ‘Thomas and Mac 
Bain. Most others which we possess are less than an inch in 
length; some having deeply-cut fronds, like our Fig. 2, and 
others comparatively little divided, like Fig. 3. All are, however, 
but pygmies to the specimens collected on the east coast of 
America, where this plant is as common as Plocamium coccineum 
is with us, and to be found as invariably ornamenting the sea- 
weed pictures made by fair Bostonians as the latter is in those 
manufactured at this side the Atlantic. On the American coast 
R. cristata commences in the Arctic Sea, and extends southward 
to Cape Cod (lat. 42°) where it suddenly disappears, as do also 
several other northern species of marine plants and animals. In 
Boston Bay it is peculiarly plentiful and-of large size, and sports 
in a number of varieties, some of which so closely resemble the 
narrower and more delicate specimens of Spherococcus coronopt- 
folius, that it requires a practised eye to distinguish them without 
an appeal to the dissecting knife. 
The most southern point in Europe at which this plant has 
been found is Berwick Bay (lat. 55°45’), and there I believe it 
has been taken but once. ‘This affords a remarkable contrast to 
its southern limit in America. 
Fig. 1. RuopYMENIA cRisTaTa:—natural size. 2. A small frond, somewhat 
magnified. 3. Another, of a broader variety. 4. Apices of lacinize with im- 
bedded tetraspores. 5. Tetraspores. 6. Section of a coccidium. 7. Spores. 
8. Thin slice, to show internal structure of the frond :—all magnified. 
