18 SEEDS 
one of the sections in water under the low power, press 
the cover-glass lightly with a needle directly over the 
section, and note that globules of oil ooze out. Do you 
find any starch or proteid? Crush a small piece of both 
seeds on glazed paper with your scalpel and note the oil. 
What is manufactured from castor-beans? Mention sev- 
eral other seeds that contain oil. 
Cut sections of a cotyledon of a pea or bean, the stem 
of which is 20 to 30 cm. long. What changes have taken 
place in the cells and their contents? Starch granules 
which are considerably corroded may frequently be found. 
Draw one. 
Ask the instructor for six unknowns, each of which 
may contain one or more of the different kinds of starch 
you have studied, and also proteid. Ascertain the con- 
tents of each. Record your results and report to the 
instructor. 
Mount a few cotton fibers, Note that each fiber is 
composed of a thin long cell, containing a very small 
cavity and a thick cell wall. The wall is composed 
largely of a substance called cellulose. Add strong iodin. 
What effect does it have on the cells? Remove the iodin 
with blotting paper and ask the instructor to add a few 
drops of 75 per cent. sulfuric acid. Be exceedingly. care- 
ful not to get acid on the microscope table, cleaning 
cloth, or hands or instruments. Study under.the low | 
power only. How does the acid affect the color of the 
cell walls? What is the final effect of the acid on the 
cells? When a substance takes on the color you obtained 
in the walls of the cotton fibers after adding iodin and 
sulfuric acids it contains cellulose. 
SS orn 
