OF THE DESMIDIACE^E AND SIMILAR MINUTE ALG^E. 51 
out pressing the Sphagnum with his hand, and then wrap 
the tuft in a piece of oiled paper or oilskin, or better perhaps 
india-rubber sheeting. 
On reaching home the Desmidiacese must be washed out 
of the Sphagnum into a glass, where they will speedily 
settle on the sides and bottom, and then the water may be 
slowly and carefully decanted. If the Desmids obtained 
by this simple process are free from mud and sand, nothing 
remains but to place them, with a camel’s hair pencil, on a 
slip of glass, as was recommended to be done with the 
Diatomacete. 
When they occur as a green stratum on the bottom of a 
pool or ditch, they may be taken up with a spoon and placed 
in a wide-mouthed bottle, while the floating specimens can 
be caught with the 1 tea sieve,’ described at p. 5. On 
turning the contents of the phial into a white dinner plate, 
the Desmids will, in a short time, collect on the surface and 
sides, and then may be gathered up with a hair pencil, and 
laid on a glass slide in a pure condition. A second 
gathering may be made by pouring off the water and 
earthy deposit, when numbers of them will be found still 
clinging to the plate. 
They may also be separated from mud and sand by 
Okeden’s method, mentioned at p. 20 ; and the collector 
has the additional advantage, in this instance, of having 
them sorted into larger and smaller specimens. 
In short, most of the arrangements in use for cleansing 
the Diatomaceas are equally applicable to the plants before 
us, provided neither heat nor acids be brought into play ; 
for the Desmids, having a membranous envelope entirely 
destitute of silica, cannot withstand the action of fire, or 
the corrosive operation of an acid, like the flinty coated 
Diatoms. 
The greater number of the Desmidiacese are free, as may 
be seen from the examples in Plate xi. figs. 50 to 53. 
In other cases we find several individuals grouped 
together in the form of a star or disk, see Plate xii. 
