12 PROTOPLASM AND PLANT CELLS 
20. Leucoplasts are colorless plastids occurring in the 
parts of the plant not exposed to light. When exposed 
to light they usually produce chlorophyll and become 
green, showing that they are essentially the same as the 
chloroplasts. They are abundant in parts of the plant 
where starch is being stored up. 
21. Chromoplasts are found in the cells of many 
flowers and fruits and other colored parts of plants. 
They are small, round or angular or needle shaped 
plastids, mostly red or yellow in color. They contain 
carotin or other coloring matters but no chlorophyll. 
In many cases they are directly developed from chloro- 
plasts by the loss of chlorophyll and the development of 
some other pigment. 
Laboratory Studies.—(a) Mount a leaf of moss and examine 
for chloroplasts. 
(b) Soak a few moss leaves in strong alcohol for twenty-four 
hours and note the decoloration of the chloroplasts, 
(c) Examine Spirogyra for spiral, ribbon-shaped, or Zygnema 
for star-shaped chloroplasts. 
(d) Soak a handful of leaves in alcohol for several hours. If 
the flask containing the alcohol and leaves be placed in hot 
water the extraction of the chlorophyll will progress more 
rapidly. Note the green color of the extract. Add a little 
gasoline or benzine (not benzene, i.e. benzol) to the alcoholic 
solution and shake thoroughly and then let it stand until the 
alcohol and gasoline separate. The chlorophyll will be found 
now in the gasoline, the carotin remaining in the alcohol. 
(e) Examine the cells of various fungi, e.g. toadstools, 
puffballs, molds, ete., or of a parasitic flowering plant, e.g. 
dodder (Cuscuta), and note the absence of chloroplasts. 
(f) Sprout a potato in darkness. Make a section of its stem 
and compare with a similar section of the stem of a potato 
grown in light. Note the leucoplasts in the former and the 
chloroplasts in the latter. Similarly compare the stomatal 
guard cells of the epidermis of green and blanched celery. 
(g) Examine the cells of a carrot root for chromoplasts 
