32 Dr George Lawson on Lemania variegata of Agardh. 
botany than in the other branches of science,” embraces 
three species of aquatic alge of very remarkable aspect and 
structure, which grow attached to stones, rocks, wood, &c., 
in the bottoms of shallow, rapid, fresh-water streams. Un- 
like most fresh water alge, they have dense compact tissue, 
giving them firm consistence ; they are rich in nitrogen, and 
when burned yield ammoniacal vapours. The plant usually 
consists of a little tuft of stiff erect or curved bristle-like 
fronds, which adhere by a common discoid root to sub- 
merged 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 con- 
tribution that has been made to the history of Lemanie, is 
the remarkably lucid description of Dr W. J. Thomson, in 
the Transactions of the Botanical Society of Edinburgh, 
vol. vi. page 2438, to which I would refer observers as an excel- 
lent basis for further inquiry, although I have been unable 
(probably from my specimens being too matured) to con- 
firm some of Dr Thomson’s results. Mr Thwaites of Ceylon 
has carefully studied the early development of the frond, 
and states that the spores at first vegetate into slender con- 
fervoid filaments, with long joints containing spirally-ar- 
ranged endochroms. The filaments constitute a sort of pro- 
thallus or pro-embryo, the initial state of the plant. After 
a time thick branchlets, the germs of the perfect and per- 
manent frond, spring from the cells of the confervoid fila- 
ment; 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, car- 
tilaginous bristle-like tubes, so characteristic of the mature 
plant in this genus. 
L.variegata.—F ronds tufted, of simple bristle-like tubes, 
rigid, corneous, attenuated towards the base and 
apex, moniliform, with black or dark-brown swollen 
elliptical nodes, and pellucid, colourless, constricted 
internodes of equal length. 
“ Hippuris fluviatilis petrea nuda Virginiensis, Pluk. 
pp p 9 , 
Phyt. tab, 193, fig. 7.” (Agardh.) 
