66 
BATBACHOSPERMEJE. 
III. LEMANEA, Bory. 
Frond cartilaginous, continuous, tubular, branched, its periphery composed of two 
strata of cells, the inner stratum formed of roundish, empty, vesicated cells ; the outer , of 
minute, closely cohering, angular, coloured cellules. Fruit , tufts of seriated spores, 
attached to the inner surface of the tubular frond. (In fresh water streams and rivers.) 
The species referred to this genus are found in fresh water streams and rivers, 
attached to stones by a discoid root. They are very dissimilar in appearance from 
other fresh water algee, being of a remarkably firm fucoid substance, opake and closely 
cellular. In many respects, however, they approach Batrachospermum , near which 
genus I have long considered to be their true systemic position, an opinion which 
must be considered as confirmed by the discovery of Tuomeya , a genus of intermediate 
structure. Kutzing associates Lemanea with Galaxaura and Actinotrichia , two genera 
that appear to me to belong to Helminthocladie.e, among the Rhodospermatous groups. 
Thwaites has given in the 20th vol. of Linn. Trans, a short account of the early develop- 
ment of the frond in L. fluviatilis. The spores at first vegetate into confervoid, 
slender jointed filaments, with long joints containing a spirally arranged endochrome. 
These constitute a sort of pro-thallus, or pseudo-colytedonous condition of the plant. 
After a time thick branchlets, the germs of the permanent frond, spring from the cells 
of the confervoid filament ; they are at first wholly dependent on the cell from which 
they rise, but soon acquire rootlets at their base, and rapidly elongating grow into the 
cellular, opake, cartilaginous fronds characteristic of the genus. Kutzing, Phyc. Gen. 
t. 19, also illustrates the early development, and gives elaborate sections of the cellular 
structure of the mature frond. 
1. Lemanea torulosa, Ag.; frond tufted, subsimple or divided near the base, robust, 
nodoso-constricted at short intervals, or rqpniliform, tapering from the base to the apex. 
Ag. Sp. Alg. 2, p. 6. Act. Holm. 1814. tab. 2, fig. 1. Kiitz. Sp. Alg.p. 528. 
L. variegata , Ag.? 1. c. p. 7. 
Hab. On rocks and stones in rivers and streams. Kentucky, Dr. Short. ( v. s. ) 
Root discoid. Stems many from the same base, 4-8 inches long or more, twice or 
thrice as thick as hog’s bristle, rising from a very slender, capillary base, and gradually 
increasing in diameter upwards for about an inch, thence maintaining an equal diameter 
for | of their length, and again tapering off at the extremity ; either quite simple or 
divided shortly above the base into numerous simple branches. The frond is regularly 
constricted and swollen at intervals of from one to two lines, so as to be nodose in the 
younger, and moniliform in the more advanced state, the distances between the swellings 
as well as their intensity varying in different specimens. The walls of the tubular 
frond are thick, composed of two layers of cells, the outer layer consisting of very minute 
and closely crowded radiant, coloured cellules, whose apices unite to form the exterior 
