BOTANY. 79 
Ferns, while cryptogamic in their flowerless condition, 
agree with the Phanerogamia in having stems and leaves; 
they are therefore intermediate in their structure; the tran- 
sition forms leading from the simple water-plants, mush- 
rooms, etc., to the pines and oaks. 
ALG. 
No class of plants is more interesting than the Alge. 
Notwithstanding their very simple structure, they offer 
every variety of shape, size, and color. While many of 
them are very minute, the beauty of their form, the deli- 
cacy of their structure, and their exquisite coloring, never 
have failed to attract the attention of the microscopist. The 
Confervoid&, or green Algae, are widely distributed, every 
| pond, ditch, spring, and stream having representatives. 
The greenish matter seen on old trees, that found in bogs, 
the slime on stones in ponds, the silk-like threads of troughs, 
| the sea-weed usually seen in marine aquaria, as well as 
| innumerable other examples which might be given, serve 
| to illustrate the green Alga, or Confervoide. Among the 
green Algz we find the simplest and smallest of plants, 
the Chlorococcus viridis (Fig. 87), which, when aggregated 
in hundreds of millions, composes the greenish matter 
H clothing in layers old trees, wood palings, etc. The Chlo- 
| rococcus is a simple cell filled with granular contents. 
Under favorable circumstances each cell divides into halves 
| (Fig. 88), each half becoming a new individual; this pro- 
cess may be continued indefinitely: such is the simple 
manner of reproduction in this very minute plant. Among 
the unicellular green Algz are included the Desmidiaceze, 
which are found most often in open situations, as in the 
pools of bogs and moors. They are among the most 
beautiful of microscopic objects. Their most characteristic 
feature is that of bilateral symmetry, giving the impression 
