FRESHWATER ALGE. 197 
beautiful spectacle is unfolded tous! That which 
to the naked eye appears a mere gelatinous mass 
of shapeless filth, is found to be composed of a 
thousand delicate and exquisitely formed threads 
or filaments, which in some instances are simple 
(Fig. 17), and in others branch, radiate, and inter- 
lace like the most beautiful network. Each of 
these threads is a transparent tube filled with en- 
dochrome, or little green cells, forming different 
Fic. 17.—CONFERVA RIVULARIS. 
figures or articulations, placed at regular intervals, 
and containing minute germs floating in mucila- 
ginous matter. This internal matter is the fructi- 
fication; and may be regarded as the first and 
simplest step in that long series of changes, by 
which certain parts of the vegetable organism are 
set apart and moulded with reference to the func- 
tion of reproduction. The modes of propagation 
