GG BATBACHOSPERME^. 



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 ivater 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 algai, 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. Kiitzing associates Lemanea with Galaxaura and Actinotrichia, two genera 

 that appear to me to belong to HelMixtiiocladie^, 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. fluviatiUs. 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. Kiitzing, Phyc. Gen. 

 t. 19, also illustrates the early development, and gives elaborate sections of the cellular 

 structure of the mature frond. 



1 . LE^rxiNEA torulosa, Ag. ; frond tufted, subsimple or divided near the base, robust, 

 nodoso-constricted at short intervals, or moniliform, tapering from the base to the apex, 

 .-l^f. Sp. Alg. 2, p. 6. Act. Holm. 1814. tab. 2, Jig. 1. Kiitz. S]). Alg. p. 528. 

 L. variegata, Ag.? I. c. p. 7. 



Hab. On rocks and stones in rivers and streams. Kentucky, Dr. Short, (v. s.) 



Boot 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 I of their length, and again tapering ofi" 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 



