118 
PALMELLACEiE. 
of large size, from which they radiate. Afterwards they become detached, and then each 
is seen at the end of a mucous prolongation similar in appearance to that already 
noticed as occurring in Gloeocapsa. Mr. Thwaites compares these threads to the 
mycelium of a fungus, but regards the increase of cells by cell-division as properly an 
act of gemmation and not of true reproduction. The reproductive process in these 
plants is by conjugation of two cells, which takes place in a manner similar to that 
already noticed as occurring in Zygnemacece. A narrow connecting tube, soon enlarg- 
ing to the breadth of each cell, is formed between two contiguous cells, through which 
the contents of both cells are mixed together ; and thus a sporangium filled with a 
denser and more distinctly granular endochrome is formed, the membranes of the 
original cells being absorbed in the process. Probably at a future stage the contents 
of this sporangium are resolved into zoospores. (See Thu;. An. Nat. His. ser. 2, vols. 
2 and 3.) 
Higher in structure than Palmella, and showing some approaches to the Nostochinece, 
or even to the gelatinous Confer vace^: ( Chcetophora ) is Hy drurus, the only genus 
which we shall further describe. 
I. HYDRURUS, Ag. 
Frond fixed at base, cylindrical or compressed, elongated, branched, gelatinous. 
Structure : seriated, but separate, cellules, filled with bright-green endochrome, enclosed 
in gelatinous parallel tubes, ranged longitudinally in the frond, and surrounded by a 
common gelatinous envelope. 
Of this genus several species have been described by authors, all having a close 
resemblance to each other, and all very variable in ramification. Indeed it is almost 
impossible to fix characters by which they can be permanently kept apart ; and instead 
of adding another specific name to the already too numerous list, I prefer to consider the 
American specimens received as constituting a luxuriant variety of the best known of 
the established species. All previously recorded species or varieties of these plants are 
natives of rapid rivers and streams in various parts of Europe. 
1. Hydrurus penicillatus , var. occidentals, Harv.; frond very long (1-2 feet or 
more) much branched ; branches very irregular, scattered or crowded, wormlike, taper- 
ing to a fine point, naked or clothed with feathery villous ramuli ; cells ellipsoidal or 
pearshaped, twice as long as their diameter. 
Hab. On the rocky bottom of rivers and streams, in a strong current. Santa Fe, 
New Mexico, Mr. Fendler, February to April, 1847. (v. s. in Herb. T.C.D.) 
