OF THE DESMIDIACE.E 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 Algae (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 

 Alga? 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 Algae 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 micro scopist. The figures 

 ia Plate xiv. represent two well-established genera of this 

 group of plants. — Ed.] 



