F U K S II W A T K U A L G OF THE UNITED S T A T K S 217 



spores, apparently not mature, have a greenish-brownish tint. 1 have also received 

 from Prof. Uavenel dried al^c, \\liich, 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. :*, pi. 19, represents a part of a branch of this plant magnified 460 

 diameters. 



FAMILY BATRACHOSPERMACK/E. 



Alir:r dioipse. Thallus filamcntosus, articulatas, ramosus, aut violaceus, violacco-purpurcua 

 vrl ciLTuluo-viriilis, muco tuatricali involutus ; fills primariis rauiisque o ccllularuui serie unica 

 r. -uindi priinuria ct scriebus numerosis sccundariis parallelis continuis vrl interrnptis extcrnis com- 

 positis, aut nmmlorum fusciculis rerticillatis globoso vel snbgloboso dense conglobatis sequali 

 distnntia obsitis, aut ramulis simplicibus vel dicbotomis dense ubique vestitia. Ycgetatio 

 tcrniinalis. 



Pitccious alfjie. Thallus filamentous, articulate, branched, violet or violet-purple or bluish-green, 

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

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

 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 medullari, acccssoriis parallelis corti- 

 cata coiupositis, ramulorum fasciculis snbgloboso-conglobatis obsessus. 



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

 series, clothed with subglobosely conglobate fasciculi of branches. 



Remarks. The Batrachosperms are amongst the very largest of the fresh-water 

 alga?, 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, . 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 Batrachosperm 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. 1872. 



