306 THE HOME GARDEN 



two crops in a year would be early peas followed by toma- 

 toes, squash, or sweet corn ; or radishes, lettuce, or spinach 

 followed by lima beans, string beans, or carrots ; or string 

 beans followed by celery, cabbage set out from plants, 

 beets, or turnips. In which of these plantings do we get 

 nitrogen provided for the soil ? 



How plant food is changed into living material and food 

 for animals. A simple experiment would convince you 

 that certain garden vegetables contain foods. If you take 

 carrots, peas, beans, radishes, turnips, potatoes, or any 

 other vegetables you may choose, and test each of them 

 for starch, for sugar, and for protein (see Chapter VI), you 

 will be able to prove the presence of these food materials. 

 How did they get there? They were not in the soil 

 and they were not in the seeds in large enough quanti- 

 ties to make the amounts we find when we gather the 

 vegetables. We know the plants made them, but how? 



Experiment. To test the starch-making power of a plant in sunlight and 

 in the dark. 



Materials: A green plant. Black alpaca cloth. Wood alcohol. Iodine. 



Method: Place any small green plant in a dark room for 24 hours. Then 

 cover parts of several different leaves with strips of black cloth. Ex- 

 pose to direct sunlight for an hour or more. Pick the leaves which 

 were covered, take off the cloth, and place the leaves in hot wood 

 alcohol to dissolve the green coloring matter. When free from green 

 color, wash the leaves and place them in a solution of iodine to test for 

 starch. 



Observation: What evidence do you find in regard to the presence of 

 starch in any part of the leaf? 



Conclusion: Why do we place the plant in the dark at the beginning of 

 this experiment? What effect does sunlight have upon green leaves? 

 How do you know? What effect does absence of light have? 



The leaf a food manufactory. This experiment shows 

 us that the green leaves of plants act as factories, in which 



