1934 Journal of Applied Microscopy 



LABORATORY OUTLINES. 



For the Elementary Study of Plant Structures and Functions from 

 the Standpoint of Evolution. 



A SERIES OF FORMS TO ILLUSTRATE THE EVOLUTION OF SEX. 



XIV. Sphczrel/a pluvialis (Flotw.) Wittr. (Haematococcus). Order, Proto- 

 coccales. Family, Volvocaceae. 



Sphaerella may be found growing in rain water, drain tiles, roof gutters, pools, 

 or ponds. It is unicellular and green in color or sometimes a bright red. If a 

 culture is once obtained, it may be preserved on a limestone or sandstone rock. 

 Put the rock into the water containing the alga and after some time take it out 

 and lay it away. Whenever material for study is required the rock need only 

 be placed in fresh rain water, when a new crop will soon appear. 



1. With a medicine dropper mount some water containing Sphaerella and 

 examine under low power. Under high power study the large, green, spherical 

 cells in the resting condition. Draw. Notice the green and red coloring mat- 

 ters — chlorophyll and haematochrome. 



2. Draw an individual divided into two, and one divided into four cells. 

 How does the division take place as regards the cell wall ? Compare with Pleu- 



Fig. 4. — Life Cycle of Sphasrella. 



rococcus. Look for an individual in which the four cells are ready to break 

 through the old cell wall. The four cells form four free-swimming Sphairellas 

 which have very loose cell walls. 



3. Study the active individuals. Describe the shape, color, cell contents 

 (especially the chloroplasts and pyrenoids), and the flagella. The tiagella branch 

 out from a clear body in the pointed end of the cell and pass out through two 

 extremely minute openings in the cellulose wall. 



4. Study and describe the movement. Which end is directed forward in 

 swimming ? How long does it take an individual to pass across the diameter of 

 the field ? Suppose the diameter is three-tenths of a millimeter, how long would 

 it take the plant to travel thirty centimeters or one foot .■• Is the motion rapid 

 or slow ? How many times its own diameter does an individual move in one 

 second ? , 



5. The flagella and other parts may be seen more clearly by adding a small 

 drop of iodin solution to the water at the edge of the cover-glass. What hap- 



