78 
OF THE OSCILLATOR!.®. 
of light, &c.), the operator will observe, even without a 
lens, a dark filmy mass radiating from the common centre 
of each piece of water, and spreading equally over the 
surface. Gradually the edges are reached, and then the 
filaments bend themselves round, and follow the line of the 
circumference. To make really good preparations, the 
greatest pains must be taken not to jolt or shake the paper 
until the water is entirely dried up, and the Algas lie flat 
on the spot prepared for them. As soon as this has taken 
place, the sheet should be removed from the board, and 
divided into the several parts marked off by the pencil. 
Each of the examples is then ready to be deposited in the 
herbarium. 
The reason why it is advisable to prepare several 
specimens on a single sheet, and to fix the latter to a board 
during the operation, is, that the Oscillatorise are of an 
exceedingly fragile nature, the filaments easily falling to 
pieces, and the fragments jerking themselves off the paper, 
if the latter be crumpled and then suddenly bent straight 
again, as is sure to happen when it is laid in the her- 
barium. Now, small pieces of paper do get so crumpled, 
while they are drying, in consequence of being acted on 
unequally by the water : whereas large sheets accommodate 
themselves more readily to the contraction and expansion 
caused by evaporation ; and consequently the individual 
sections are smoother and less wrinkled when the whole is 
cut up. A single experiment will demonstrate this. 
There are certain genera, some of which belong to the 
Oscillatorian family, the members of which (instead of 
spreading themselves out like those we have just been 
speaking of) group themselves into close flocculent masses. 
Such are Phormidium, Microcoleus, some species of 
Symploca, and not a few of the Scytonemaceas ; among the 
Ulotrichse, Hormidium and Schizogonium ; and of the 
Zygnemaceas, Zygogonium. In all these forms the filaments 
have a tendency to develop themselves towards the 
interior, and their growth is exceedingly complicated in 
