84 ARCHEB; ON' ri.OSTERirM ACICT'LARE. 



culty. Through the kindness of ]M. de Brebisson I have had 

 an opportunity of comparing dried specimens of his C. pro- 

 num v.ith C. aciculare, and wliile tiiey seem to approach 

 Aery closely, I do not doubt but that they are distinct 

 species, and yet it "would be difficult to express their special 

 distinguishing characteristics. They are about equal in 

 length ; C. aciculare is perhaps slightly the longer, but the 

 specimens I possess of C. pronum are about two and a half 

 times broader at the widest part than Mr. West's specimens 

 of his C. aciculare, hence the tapering in the former species 

 is less gradual, and the colourless extremities not so pro- 

 longed, nor probably quite so slender as in the latter, nor is 

 their curvature, perhaps, quite so great. It would of course 

 be desirable to see fresh specimens of both. I have never 

 myself met with C. pronum, and specimens dried on talc may 

 not a little lose their characteristic outline. It seems to me 

 that C aciculare may be said to bear a relationship to C. 

 pronum somewhat similar to that which C. setaceum (Ehr.) or 

 C. elegans (Breb.) bear to C. rostratum (Ehr.), which are, I 

 doubt not, good and distinct species. It may, perhaps, 

 appear to some that the specimens met with by me in this 

 countiy, and which I refer to C. aciculare, and which, as 

 stated above, are slightly less slender than Mr. West's 

 specimens, might be looked on as an intermediate variety 

 connecting this form with C. pronum, but I am not disposed 

 to think so. My specimens are much more slender than 

 those I possess of C. pronum, and agree, so far as I can see, in 

 general outline with C. aciculare. De Brebisson himself, 

 judging from the figure, is disposed to think C pronum and 

 C. aciculare to be distinct; he had not, however, seen any 

 specimens of the latter. 



There seems little danger of the form under consideration 

 being mistaken for C. gracile (Breb.) (not uncommon here), 

 a species whose diameter is not greater, but its length is 

 considerably less. Instead, however, of gradually tapering 

 from the middle towards each apex, that species presents a 

 linear outline, the endochrome reaching to near the slightly 

 curved blunt extremities. Its conjugated condition, too, is 

 unknown ; but though very slender throughout the length of 

 the frond, its extremities are not prolonged in a setaceous 

 manner. 



Such, then, seems to me the state of the question as 

 regards this elegant form. I conceive that it and C. pronum 

 are distinct species ; doubtless, it might indeed eventuate 

 tliat they are but extreme forms of the same species, but I 

 should bo disposed to say that that side of the question 



