The Scottish Naturalist. 259 



few years ago I determined to search for the missing species, and, 

 with the help of a few friends, I have succeeded in adding nearly 

 100 species of marine algae to the British Flora. To Mr. G. W. 

 Traill, of Edinburgh, and Mr. E. Batters, F.L.S., of Berwick-on- 

 Tweed, I am especially indebted for the assiduous manner in 

 which they have examined the marine flora of the districts in which 

 they live. 



There are, however, still many species that probably occur on 

 the Scottish coast, but of which I have not yet seen specimens. 

 Believing that there are many algologists in Great Britain who 

 would recognise these plants, if furnished with a description of 

 their characters and an outline of their form and structure, I wish 

 to call attention from time to time, as opportunity presents itself, 

 to the seaweeds likely to occur in Scotland, and I know of no more 

 appropriate means of doing so than through the columns of the 

 Scottish Naturalist. The visit of Dr. O. Nordstedt to this country 

 during the month of July last year, directed my attention to the 

 genus Vaucheria, which, as regards the marine species, has hitherto 

 been very little investigated in Britain. The figures in Harvey's 

 Phycologia Britannica represent plants imperfectly known to that 

 prince of algologists, since, except his V. velutina Ag., they were 

 seen by him only in the dried state. 



The following remarks concerning Harvey's figures may, per- 

 haps, clear the way for further elucidation of the species of this 

 genus. 



Vaucheria marina, t. 350. A, represents Derbesia marina, Sol. 

 Ann. Sc. Nat. (3), Vol. V1L, p. 158. 



Vaucheria submarina, t. 350. B, represents only the fronds 

 bearing antheridia, of V. dichotomy var. submarina Ag. This plant 

 I have seen growing abundantly at Weymouth, where it covers the 

 mud at low water for several acres, near the Isle of Portland. Its 

 habit of growth is, however, different from that of all the other 

 marine species that I have seen. The threads are sparingly 

 dichotomous, quite erect when under water, but running together 

 into points when exposed to the air, so that a tuft of threads can 

 be taken between the finger and thumb and pulled out of the 

 black mud to the length of 2 or 3 inches. It can thus be cleaned 

 with tolerable ease. The threads stand about 1^ inch above the 

 sandy mud, and are coarse and of a dark green colour, and they 

 never form the dense, intricate, velvety cushions so common in 



