MICROSCOPIC PLANTS. 



sion. Fig. 8 is a lovely form called Closterium, found 

 in myriads at the bottom of ponds. In both these 



FIG. 7. FIG. 8. FIG. 9. FIG. 10. 



species the plant consists of two cells. In fig 1 . 9 

 (Pediastrum) there are a large number of cells united 

 into a spherical form, each cell having two processes 

 from it which give the compound plant a stellate 

 appearance. In Scenedestmis (fig. 10) the cells are 

 united side by side, and the two extreme cells of the 

 series are provided with long filaments. These all 

 belong to the order of Desmids. They are totally 

 distinct from the Diatoms which we shall allude 

 to presently but in several points they somewhat 

 resemble them. Multiplication takes place by divi- 

 sion, though in a somewhat peculiar manner. Thus 

 fig. 7 shows Cosmarium dividing ; the two outer cells 

 formed the old plant, and the inner ones are those 

 newly formed. The next change to take place would 

 be a division between the two new cells, and thus 

 two separate plants would be formed, each consisting 

 of a new and an old cell. The same process goes on 

 in the other Desmids. The Diatoms (figs. 1 1, 12, 13) 

 are all encased in little boxes, composed of pure 

 flint formed into two valves, one of which fits into 

 the other, just as a pill-box fits into the lid. They 

 are not green like the Desmids, but yellow-brown. 

 Like Volvox, the Desmids, and other plants, the 

 Diatoms have been claimed as members of the 



