The colour varies from pale yellowish, in shallow water, to various degrees 
of livid purple, in deeper and more shaded situations. In fresh water the 
plant soon decomposes, giving out a pinkish dye of some brilliancy. 
A very common plant, and one which, though tolerably con- 
stant to a particular ramification, having long simple branches 
springing from a simple stem, is yet subject to many modifymg 
causes, which affect its habit, and general appearance very con- 
siderably. ‘The variety 8, an excellent figure of which is given 
by Dr. Greville, im his ‘ Crypt. Flora,’ differs extremely from the 
normal form, represented in our plate. In it, the frond is often 
an inch in diameter, and so much puckered and waved, that, 
except in colour, it strongly resembles Exteromorpha intestinalis. 
Yet this variation appears to arise solely from locality, bemg 
always found where a strong stream rolls down. 
Dumontia filiformis is widely dispersed in the temperate zones, 
and was found by Dr. Hooker, both in the Auckland group of 
Islands, and at the Falklands. Throughout Europe it is ex- 
tremely common. ‘There are several other species of the genus, 
many of which are found in the Kamtschatkan seas, and along 
the opposite coast of America. One of them, D. saccata, which 
has a simple, bag-like frond, is found, if all the plants which go 
under this name belong to one species, in localities nearly as 
widely apart as is D. filiformis, occurring on the west coast of 
America, and at the Cape of Good Hope. Another species, D. 
prismatica, J. Ag., inhabits the Indian Ocean. But the generic 
characters of several of the reputed species, require examination, 
and, probably, many will eventually be removed to new genera. 
The Dumontie are the most simple in structure of the Gasfero- 
carpe@, in which they represent such plants as Hnteromorpha, 
Asperococcus, &e. They are also found at a higher level than any 
others of their family, some of them growmg, as our common 
one occasionally does, nearly at high water mark. 
Kiitzing figures and describes ¢etraspores on this species, but I 
have not had the good fortune to find them. . The clustered 
spores are common. 
Fig. 1. Dumontra rrLirorMis :—vnatural size. 2. Portion of the frond, showing 
a front view of a cluster of spores, attached to the inner surface. 3. Lateral 
view of the same cluster, and vertical section of the wall of the frond :— 
magnified. 
SS 
