114 BOTANY. 



Protococcus resemble other protophytes. By fission the 

 cells are divided into two or four new ones, and this ap- 

 pears to he 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 (ChroOcoccus, 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. 



(J) In midsummer look along the water-line of f rcsh-wiiter lakes 

 and ponds for soft, amber-colored, rounded masses from the size of a 

 pea to that of a hickory-nut. By mounting a sm.ill 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 helerocyst), 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 tlie microscope. 



((i) 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 heibarium specimens for 

 future study. Tlie Slime Moulds should be kept dry in little pill- 

 boxes. The filamentous Green Slimes may bo floated out upon sheets 

 of paper as described in (j) on page 129. 



(/) 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. 



