70 A LABORATORY MANUAL OF BOTANY 
Oscillaria 
General study.—Observe plants in horse-troughs, stag- 
nant pools, and in dishes in the laboratory. Note the free 
ends of filaments standing out from the supporting sub- 
stance. Note the color. 
Vegetative structures.——Mount a little of the material. 
Study the general form of the plants, and note the slow 
gliding or swinging movement. Is this movement in any 
definite direction? Can you determine whether the move- 
ment is caused by currents of water? What is the form of 
a single Oscillaria cell? How are cells arranged in forming 
the plant? Is there any protection about the cells? Note 
the end-cell of a plant, and account for any peculiarities. 
Reproduction.—In reproduction this plant resembles 
Nostoc. There is usually no specialized cell assisting the 
plant in its division, but division may occur at any place, 
each new part becoming a new plant. Select specimens 
showing how the reproduction takes place, and draw. 
LESSONS XXXVI AND XXXVII 
Spirogyra 
General study.—This species of alga is often seen float- 
ing on the surface of rather quiet water, where it makes a 
mat ranging in color from very bright green to brownish 
green. Examine carefully some plants which have been 
placed in an aquarium. How would you distinguish 
Spirogyra from the plants already studied? 
Vegetative structures—With the forceps remove and 
mount a few of the plants. Note how the cells are arranged 
to make up the plant. How do the cells compare in size and 
form with those of plants previously studied? Is there a 
sheath about all the cells of one plant? Can you determine 
whether the ends of a plant are alike? If unlike, this might 
