114 BOTANY. 
Protococcus resemble other protophytes. By fission the 
cells are divided into two or four new ones, and this ap- 
pears to be the more common mode of increase. They also 
produce new cells by internal cell-formation similar to that 
in the yeast-plant. 
Practical Studies.—(a) Scrape off a little of the greenish slimy mat- 
ter from a damp wall, mounting it in water: examine under a high 
power. Some small blue-green or smoky-green cells will be found 
belonging to the lower Green Slimes (Chroécoccus, etc.); of these 
some will probably be found in process of fission. Larger bright- 
green cells filled with granular protoplasm will also be found: these 
are a species of Protococcus. 
(0) In midsummer look along the water-line of fresh-water lakes 
and ponds for soft, amber-colored, rounded masses from the size of a 
pea to that of a hickory-nut. By mounting a small slice of one of 
these, it will be seen under the microscope to be composed of myri- 
ads of filaments of Nostoc similar to A, Fig. 49. Occasionally a fila- 
ment may be seen with a larger cell (a heterocyst), as in the figure. 
Its function is not known. 
(c) Secure a handful of the dark-green filamentous growth which 
is common on the wet sides of watering-troughs, and place it in a 
dish of water. If it is an Oscillaria it will rapidly disperse itself, an 
hour being long enough to show quite a change in position. Now 
mount a few filaments in water and examine under a high power. 
They will be seen to sway from side to side, and to move quite rap- 
idly across the field of the microscope. 
(d) In midsummer scrape off one of the small jelly-like masses of 
Rivularia, so common on the submerged stems of water-plants, mount 
in water, crushing or cutting the mass so as to show the individual 
filaments. Each filament tapers from the centre of the mass out- 
ward, and at its larger end there is generally a larger cell (a hetero- 
cyst). 
(e) Some protophytes may be preserved as herbarium specimens for 
future study. The Slime Moulds should be kept dry in little pill- 
boxes. The filamentous Green Slimes may be floated out upon sheets 
of paper as described in (j) on page 129, 
(f) It is always desirable to preserve some of the aquatic proto- 
phytes in weak alcohol for future study. Reduce the alcohol to one 
fourth or one fifth strength. 
