310 A Rare British Freshwater Alga. [Sess. 



1\\.—A BABE BBITISH FBESHWATEB ALGA. 



By Mr JOHN LINDSAY. 



{Bead Dec. 21, 1910.) 



Between the years 1823 and 1828 there was published in 

 our city of Edinburgh a work in six volumes which deserves 

 to be had in grateful remembrance by all students of Botany 

 — viz., ' The Scottish Cryptogamic Flora ' of Dr E. K. Greville. 

 This book was, in fact, meant to be a continuation of Smith 

 and Sowerby's ' English Botany,' taking up those groups which 

 had been omitted from that well-known authority, — the Fungi, 

 the Algae (including the Diatomacese), and the Mosses. When 

 compared with the manuals of the present day dealing with 

 these groups, the great progress made since Dr Greville's time 

 is very apparent; yet his six slender volumes, with their 

 beautifully coloured plates, are a remarkable production for 

 that early date, and fetch a considerable price when a com- 

 plete copy comes into the book-market. By a lucky accident, 

 so to speak, the subject of this paper is enshrined in Dr 

 G-reville's sixth and last volume. About fifteen years before 

 the publication of ' The Scottish Cryptogamic Flora ' a floating 

 Alga had appeared in The Haining Loch, Selkirk, and in 1828 

 it was perceptibly increasing. The proprietor, at that period, 

 of The Haining sent specimens of this Alga to Dr Greville, 

 who, in his work just mentioned, writes of it thus : — 



" I am indebted to the kindness of John Pringle, Esq. of 

 The Haining, and Captain Gordon of Eccles, for specimens of 

 this plant, accompanied with an account of its appearance in 

 the lake. The lake itself is a natural sheet of water, cover- 

 ing an extent of about thirty-five acres, of from three to fifteen 

 fathoms in depth, and supplied partly by rivulets and partly 

 by a bottom spring. During summer, however, these are 

 nearly dry, and the lake is consequently in a state of more or 

 less stagnation, which is doubtless highly favourable to the 

 development of Algae as well as of Animalculae. 



" The plant in question has been remarked for a period of 

 twelve to fifteen years, during which time it has gradually but 



