OF THE DESMIDIACEiE AND SIMILAR MINUTE ALG^E. 61 
' family in the whole range of the plant world which pre- 
sents such a boundless variety of forms, and consequently 
none in which mistakes and confusion may more easily 
arise from neglect of this precaution. 
There are certain minute Alga3 (of which Aphanizomenon 
is an example), members of the Confervoid order, which 
float on the surface of the water, forming a delicate mucous 
film. These may be most conveniently secured by scooping 
them up with the tin ladle described at p. 4, and pouring 
them into a linen net. As the water passes away, the 
Algse are left behind, and as soon as a sufficient quantity 
is obtained, they may be scraped off into a bottle, to be 
conveyed home. 
The specimens of Aphanizomenon should be mounted 
as speedily as possible (it is best done on the spot), because 
the faggot-like bundles of filaments quickly separate and 
fall asunder. If it is desired to retain the true habit of 
the plant, it ought to be caught at once on paper, and 
allowed to dry without delay. By exposing the dried 
specimens for some days to the light and air, the yellowish 
colour which they possessed during life passes into a 
brilliant green tint. 
[Though scarcely to be reckoned among ‘collectors’ 
plants,’ I cannot omit mention of the Volvocinese among the 
minute Algse placed, for convenience sake, in this chapter. 
Their singular motions — for most of them move freely 
through the water with the aid of cilia — their peculiar 
forms, and wonderful modes of propagation, render them 
objects of great interest to the microscopist. The figures 
in Plate xiv. represent two well-established genera of this 
group of plants. — Ed.] 
