Oo UI > 
Black sateen cloth bags made of two layers of cloth large enough to 
hold at least two dishes. 
Dark-blue cellophane. 
Fluorescent lamp (a fluorescent desk lamp will do). 
Seeds of several kinds of plants, including several varieties of lettuce 
and tomato. 
Procedure: 
OR WN Re 
Prepare dishes as previously described in demonstration A-2. 
Distribute 100 seeds evenly on the blotters of each dish. 
Dish 1 is placed in a black cloth bag (darkness), 
Dish 2 is placed under the fluorescent lamp. 
Dishes 3 and 4 are completely covered with two layers of dark-blue 
cellophane and placed under the fluorescent lamp. 
The fluorescent lamp is left on continuously. 
After germination is apparent in dish 2, count and record the number 
of germinated seeds in all dishes, 
Re-cover dish 3 with the blue cellophane and replace both dishes 3 and 
4 (without cellophane) under the fluorescent lamp. 
When germination is completed in dish4, countand record the germinated 
seeds in both dishes 3 and 4, 
Observations: 
The seeds in the dishes under the dark-blue cellophane may not germinate, 
whereas those receiving either light or darkness may germinate nearly 100 
percent, After a dish has remained under blue cellophane in light for 3 or 4 
days it can then be covered with black cloth and the seeds may remain 
dormant in the dark. When subsequently given unfiltered light, they promptly 
germinate. 
Supplementary Reading: 
See Demonstration A-1l1, 
DEMONSTRATION A-5: Photoreversible control of seed germination by red 
and far-red light. 
Materials: 
1, Three petri dishes or plastic sandwich boxes with lids. 
2. Ordinary color-fast or white blotters, filter paper, or paper towels. 
3. Red and dark-blue cellophane, 
4, Black sateen cloth bags made of two layers of cloth large enough to hold 
Or 
each dish, 
Light-sensitive seeds such as Grand Rapids lettuce or peppergrass 
(Lepidium virginicum). 
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