FRESU WATER ALG^ OF THE UNITED STATES 217 



spores, apparently not mature, liave a greenish-brownish tint. I have also received 

 from Prof. Ravenel dried algte, which, apparently, are the same species as those 

 from which this description has been written, but which, not being in fruit, cannot 

 be absolutely identified. They are, as dried, of a bright bluish-green, and attain 

 the length of an inch and a half or more. 



Fig. 3, pi. 19, represents a part of a branch of this plant magnified 460 

 diameters. 



Family BATRACHOSPERAIACE^. 



Algae dioics. • Thallus filamentosus, articulatus, ramosus, aut violaceus, violaceo-purpurcus 

 vel caeruleo-viridis, muco uiatricali involutus ; fills primariis ramisque e cellularum serie unica 

 central! primaria et seriebus numerosis secundariis parallelis contiuuis vel interruptis externis cora- 

 positis, aut ramulorum fasciculis verticillatis globoso vel subgloboso dense conglobatis a;quali 

 distantia obsitis, aut ramulis simplicibus vel dichotomis dense ubique vestitis. Vcgetatio 

 tcrminalis. 



Disecious algte. Thallus filamentous, articulate, branched, violet or violet-purple or bluish-green, 

 covered with mucons; primary filament and branches composed of a single central series of cells, 

 and numerous external, parallel, continuous, or interrupted secondary series; either furnished with 

 globosely or subglobosely densely conglobate, equally distant verticillate fasciculi of branches, or 

 everywhere densely covered with simple or dichotomous branches. Vegetation terminal. 



Genus BATRACHOSPERMUM, Roth, 1800. 



Thallus filamentosus, moniliformis, e cellularum serie unica meduUari, accessoriis parallelis corti- 

 cata conjposltis, ramulorum fasciculis subgloboso-conglobatis obsessns. 



Thallus moniliform, composed of a simple series of medullary cells and cortical accessory parallel 

 series, clothed with subglobosely conglobate fasciculi of branches. 



Remarha. — The Batruclioapcryns are amongst the very largest of the fresh-water 

 algae, forming gelatinous branched masses from a few inches to even more than a 

 foot in length. The fronds are very freely and very irregularly branched, and are 

 evidently composed throughout, i. e., both in regard to the main filaments and the 

 branches, of two portions, a central axis and much more slender short transverse 

 branchlets, which often end in a long hair, and are arranged more or less exclu- 

 sively in groups, so as to form, to the naked eye, at regular intervals, little balls or 

 knots, the whole plant thus presenting a sort of moniliform aspect. Sometimes, 

 however, these glomeruli are placed so closely together, and grow so large that 

 they become confluent, and the branch to which they are attached appears as a 

 uniform thick and very gelatinous cylindrical cord. 



The axis both of the stem and the branches of a BatracTiosperm consist ori- 

 ginally of but a single series of cells. The development of new cells takes place 

 in two ways, the one of which results simply in an increase in the length of the 

 axis, the other in the production of branches. The first of these is the ordinary 

 process of cell multiplication by division, and occurs only in the end cells, so that 

 no new cells are ever formed in the central portions of the axis, which increases 

 in length solely by the addition of new cells at the end, and by longitudinal growth 

 of the old ones. The first step towards the formation of a branch is the produc- 

 tion of a little pouch-like protrusion near the upper end of a cell. This increases 



28 September, 1873. 



