NEW OR CRITICAL BRITISH ALGJ2. 
115 
and the plant undoubtedly belongs to the genus Urospora , which, 
before Mr. Robertson’s discovery, was only presumed to be the 
case. 
The Cumbrae plant agrees in every way with the type specimen 
(gathered by Sir W. Hooker in 1808, and now preserved in the 
herbarium of Trinity College, Dublin), from which both Dillwyn’s 
and Harvey’s descriptions were drawn up. The cells in the small 
portion of the type which I examined varied in diameter from 
10-420 p, but probably thicker filaments were present in the tuft, 
and were just as various in form as are those of the Cumbrae 
specimens. 
Out of Britain this species has been recorded from the North 
Sea by Kiitzing, from Cherbourg by Le Jolis, and from Nahant, 
Mass., by Farlow. It was “ with considerable doubt ” that Prof. 
Farlow referred the American specimens, gathered by M. F. 
Collins, to U . collabens ; and judging from the specimens which have 
since been distributed in the Phykotheka universalis (No. 431), I 
am inclined to think they are referable to the Conferva bangioides 
of Harvey rather than to his C. collabens. Harvey founded his 
Conferva bangioides on some specimens gathered at Torquay by 
“Mrs. Griffiths, to whom belongs the merit of having determined 
its characters correctly.” I have examined these specimens, and 
find that they agree in almost all respects with M. Collins’s 
Nahant plant. The filaments are from 5 to 6 inches long, and of 
a deep green colour, the cells 30-150 p in diameter (usually 
40-90 p), and from 50 to 230 p long, usually twice or thrice, but 
occasionally 5 times longer than broad, the nodes slightly con- 
stricted. These measurements were, of course, made from a 
remoistened specimen ; those taken from fresh plants would pro- 
bably be slightly greater. 
Both Farlow (Mar. Alg., New Eng., p. 45) and Hauck (Meeres 
Alg., p. 443) give the diameter of the filaments of U. collabens as 
50-180 p , which is very nearly the same as in the type specimens 
of U. bangioides , with which their descriptions agree in other 
respects. 
Kiitzing (Spec. Alg., p. 383) gives the measurements of his 
Hormotrichvm collabens as 50 p at the base, and 115-150 p at the 
apex. On the other hand, he gives the diameter of the filaments 
of H. Younganum (= Urospora isogona) and H. bangioides as 
28-75 p. 
Mrs. Griffiths’s Torquay specimens of U. bangioides are mixed 
with Urospora isogona (===H. Younganum ), as is usually the case 
with that species, and it is probable that the specimen sent by 
Harvey to Kiitzing was principally composed of U. isogona , and 
that Kiitzing examined only filaments belonging to that species ; 
this would account for his doubting whether H. Younganum and 
H . bangioides were really distinct, for he certainly was not, as a 
rule, given to “ lumping.” On the whole, it appears to me that 
the Ulothrix collabens of Farlow and Hauck, and the Hormotrichum 
