OF THE DESMIDIACEiE 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 Desmidiaceae 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 

 Diatoinaceae. 



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 

 iaa wide-mouthed bottle, while the floating specimens can 

 be caught with the ' 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 Diatomaceae 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 Desmidiaceae 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 xn. 



e 2 



