LAWSON"— ON LEMANIA, 3T 



usually consists of a little tuft of stiff erect or curved bristle -like 

 fronds, whicli adhere by a common discoid root to submerged 

 objects. The minute structure of these plants has been illustrated 

 very fully by authors at different times, from Vaillant (1727) 

 downwards, with singularly conflicting results. The most recent 

 and perhaps most valuable contribution that has been made to the 

 history of Lemanice, is the remarkably lucid description of Dr. W. 

 J. Thomson, in the Transactions of the Botanical Society of Edin- 

 burgh, vol. vi. page 243, to which I would refer observers as an 

 excellent basis for further inquiry, although I have been unable 

 (probably from my specimens being too matured) to confirm some 

 of Dr. Thomson's results. Mr. Thwaites of Ceylon has carefully 

 studied the early developement of the frond, and states that the 

 spores at first vegetate into slender confervoid filaments, with long 

 joints containing spirally arranged endochroms. The filaments 

 constitute a sort of prothallus or pro-embryo, the initial state of 

 the plant. After a time thick branchlets, the germs of the perfect 

 and permanent frond, spring from the cells of the confervoid 

 filament ; they are at first wholly dependent upon the cell from 

 which they rise, but soon acquire rootlets at their base, and, rapidly 

 elongating, grow into the densely cellular, opaque, cartilaginous 

 bristle-like tubes, so characteristic of the mature plant in this genu5. 



1. L, fluviatilis, iuteTVLodes longer than nodes=(Confervia fluvlatilis 



lubrica setosa, Equiseti facie, Horse-tail River Conferva, Dillemus, 

 Hist. Muse, tab. vii. fig. 47. Conferva fluviatilis, Linn.^ 31ohr, 

 Both., &c. Poljsperma fluviatilis, Vauch. Chantransia fluviati- 

 lis, DC. Lemania corollina, -Bory. Nodularia fluviatilis, iyw^rJ.) 

 This is the more common British species which I gathered in 

 quantity in a stream on the Ochil Hills, near Stirling, in 1857. 

 It has also been recorded as growing near Bangor {Dillenius), in 

 Winterbourne Stream, Lewes {W, Borrer); at Hamsell, and at 

 the waterfall at Harrison's rocks (^. t7e?i?zer); Aberdeen, abun- 

 dant (^Professor Dickie, 3I.D.); Ireland, frequent (Z). Moore); 

 Scandinavia, Germany, France, Corsica ; Sackville river, Nova 

 Scotia, adhering to stones. 



2. !*• tuberculosa = (Nodularia fluviatilis ramosa, Lyngb.) Denmark, 



3. y- media = (Conferva fluviatilis, Dillw., E.B., t. 1763), England. 



4. ^. /wci'/ia =[(Lemania fucina, 5ory, Chantransia dichotoma, DC.) 



France, chiefly in Bretagne, 



5. «• subtilis = (Lemania subtilis, Agardh, in Act. Holm. 1814, t, 2, 



f. 4, Kutzing.) Sweden, &c. 



