168 PHYLUM I. MYXOPHYCEAE 



these some will probably be found in process of fission. Larger 

 br'ght-green cells filled with granular protoplasm will also be 

 found; these are species of Protococcus belonging to the next 

 phylum. 



(b) In midsummer look along the water-line of fresh-water 

 lakes and ponds for soft, amber-colored, round 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 myriads of filaments of Nostoc. Occasionally a 

 filament may be seen with a heterocyst; 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 an Oscillatoria, it will rapidly 

 disperse itself, a few minutes 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 while moving quite rapidly 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 center of the mass outward, and at its larger (inner) 

 end there is generally a heterocyst. 



Some elementary studies of bacteria may be made very easily, 

 but their profound study (Bacteriology) involves a technique 

 v/hich is unattainable by the beginner in Botany. The follow- 

 ing may be attempted. 



(e) Boil a pinch of cut hay or any other similar vegetable 

 substance for a few moments, and put into a glass of water; 

 keep in a warm room for a couple of days, or until it be- 

 comes turbid (from the abundance of bacteria) ; examine a 

 minute drop with the highest powers of the microscope, for 

 active bacteria. The bacterial growth originates from the 

 spores which were not killed by the short boUing. The com- 

 monest form thus obtained is Bacillus subtilis. 



(/) Put a bit of fresh meat into water, and study the bacteria 

 which will appear in it. Spiral forms (especially Spirillum) 

 may often be found in such a preparation. 



{g) Exiimine the juices of decaying fruits and vegetables. 



