TAXONOMY 
227 
3. Reducing and Strengthening Bath: 
Gallic acid. 5 
Tannin. 3 
Fused sodium acetate. 10 
Distilled water. 350 
The flamed cover glass is first covered with the mordant for one- 
half hour, or if in a thermostat at 5o°C. for- five to ten minutes. 
The mordant is then carefully removed by thorough washing in 
water, alcohol and water. The coyer (film side up) is now put into 
the silver bath (a few mils in a clean beaker or watch glass) for a 
few Seconds, during which time it is gently agitated. Without 
rinsing it is next put into a few mils of the reducing solution and 
gently agitated until the fluid begins to blacken. It is then washed 
in water and examined. If not stained deeply enough the cover is 
returned to the silver bath. It is finally dried and mounted in 
balsam. All the dishes must be scrupulously clean. The fluids 
must not be contaminated by the fingers nor by dipping iron or 
steel instruments into them. 
Broca’s Differential Stain.—- 
Loffler’s Methylene Blue. 80 mils 
ZiehPs Carbol Fuchsin. 10 mils 
Mix the solutions. 
This stain differentiates between dead and living bacteria. Dead 
bacteria take on a red coloration and living bacteria a blue color. 
2. Cyanophyce^e 
Plants which are sometimes termed blue-green algce. They con¬ 
tain chlorophyll, a green pigment, and phycocyanin, a blue pigment, 
a combination giving a blue-green aspect to the plants.of this group. 
Found everywhere in fresh and salt water and also on damp logs, 
rocks, bark of trees, stone walls, etc. Examples: Oscillatoria , Glce- 
ocapsa, and Nostoc. 
Gloeocapsa.—This blue-green alga is commonly found on old, 
damp flower pots in greenhouses and on damp rocks and walls 
