74 
OF THE FILAMENTOUS ALGJ2. 
than is the case with the greener and more compact portions 
of the tuft. Specimens of the conjugating filaments should 
always be obtained, if possible, as the characters of several 
of the genera are based upon this curious phenomenon. I 
may mention among others Mougeotia, Mesocarpus, Pleuro- 
carpus, Craterospermum, Staurospermum, Ehynconema, and 
Spirogyra. In all these the sterile filaments are of little 
service in affording generic characters, whereas (except 
in the one mentioned last) the presence of conjugating 
examples marks the genera at once, even after they are 
dried. 
Another remarkable phenomenon, the so-called 4 Swarm- 
ing Spores,’* common to all the filamentous Algas, is most 
easily observed in the species of Ulothrix. The escape of 
the Zoospores from the parent cell generally takes place in 
the early part of the day, and betrays itself even to the 
naked eye by a green film which forms on the water’s 
edge when the Algce are kept in a glass vessel. It may be 
observed, too, in the (Edogoniacese, especially in CEdogo- 
nium fonticola, in which the swarming spores may be seen 
at almost any period of the year. The cilia with which 
these spores are furnished defy detection on account of the 
almost incredible swiftness of their movements ; but they 
may be seen easily enough if a drop of solution of iodine f 
be allowed to work its way by capillary attraction under 
the covering glass. As the solution mixes with the water, 
it paralyses and finally kills every object of an organic 
nature with which it comes in contact. While this is 
taking place, the observer must keep his eye fixed upon the 
dying spores, applying a rather oblique — at any rate not 
too bright — illumination, and then he will see the glistening 
threads as they swing to and fro. 
Many of the Cladophoras, Confervas, and (Edogonias, 
* It takes its name from a fancied similarity of the movements of 
the Zoospores in the parent cells to the swarming of bees. — Ed. 
t Either iodine dissolved in alcohol, or an aqueous solution of 
iodide of potassium. 
