68 
CONFERVACEiE. 
filaments are enclosed within a common gelatinous envelope, and thus formed into 
somewhat compound fronds. In the great hulk of the Order no fructification other than 
minute zoospores has been observed. These are formed out of the colouring matter of 
the cells, are furnished with vibratile cilia, and when they escape from the cell in which 
they have been organised, enjoy for a time active powers of locomotion. At length fixing 
thfemselves to some object they change their form, becoming cylindrical ; and then, 
dividing repeatedly, are changed into articulated filaments similar to those of the parent 
plant. In the Confervce the frond lengthens in two ways ; either by the repeated 
bisection of all the cells of the frond, as is usually the case in the unbranched species ; 
or by the evolution of new cells, constantly at the apex of the terminal cell, as is com- 
mon in the branching species. In these latter the cell, after having once formed one 
or more new cells out of its apex by a cutting off of the summit from the basal portion, 
remains unchanged, without further growth or cell division. If but one new cell be 
formed at the apex, the filament will be simple ; but in the branched species two or 
more cells are formed, the central one continuing the frond, while the lateral ones, which 
spring just below the summit of the old cell, grow out into branches. 
The Confervaceas are almost universally dispersed in water of every character 
found on the surface of the globe. Many are marine, but perhaps the largest number, 
at least of individuals, if not of species, are found in fresh water. The marine species 
usually grow within tidal limits, but several of the Cladophorae occur in the Laminarian 
zone, and some even at a greater depth. The fresh water species are found in lakes 
and ponds, in rivers, streams, and wells, and in thermal springs or in mineral waters. 
A large number of genera and species have been described ; but I fear the proper 
number of both genera and species has been much exaggerated, and that multitudes 
must be erased from the list whenever the Order shall be carefully revised. The fresh 
water species have as yet scarcely been attended to in America. I have received very 
few of these, and most of them in a state unfit for examination. Indeed, dried specimens 
of such obscure algse are of little value for determining species. A few of the more 
remarkable are here described ; being all those that I can clearly make out from the 
specimens received. It is, however, often a difficult task either to refer one of these 
species to its supposed type, or to devise specific characters that shall not be illusory 
for what appear to be new forms. The characters usually insisted on, namely, the 
length of the cells as compared with their diameter, the absolute diameter of the cell, 
and the degree of ramification of the filament, are all subject to much variation. There 
appear to be no definite limits to any of these characters in any species. We are 
forced therefore, in describing" them, to be content with rude approximations. Figures 
are of little use, for in many of the species, such as Chadopliora glomerata , scarcely two 
specimens are in all respects similar. 
