EXERCISE 4 



THE SEED AS A SOURCE OF PLANT FOOD 



Statement. The seed contains, in addition to the miniature plant, the food upon which the plant 

 lives during the days when the seed is germinating, and until the young plant has unfolded its leaves 



in the sunlight and air and its roots have become firmly estab- 

 plantiet ft ^ ^ lished in the soil. If, after the food which is necessary to nourish 



the plant through these periods is consumed there remains a reserve 

 to help the young plant get along while it is delicate, the chances of 

 the plant's living and producing a satisfactory harvest are greatly 



increased. 

 Fig. 6. Ratio of embryo to stored food 



a, cross section of bean ; b, cross section of corn Object. To show the relationship of the stored food in the seed 



to the seedling. 



Materials. Eight flowerpots or tin cans ; sand ; corn kernels; lima beans; potatoes. 



Directions, i. In a pot of sand plant four kernels of corn, and in another plant four kernels of corn 

 prepared by paring away all of each kernel except the soft, oily germ which lies on the concave side of 

 the kernel. In a third flowerpot plant four lima beans. Water the three pots alike and place them 

 where the plants can grow to the best advantage. As soon as the beans come up remove all but two 

 of the plants. When the seed leaves on one of the plants begin to spread apart, and the little plant 

 appears between them, remove the seed leaves by use of a sharp knife. Leave the other plant unmo- 

 lested. Observe them after a few days. 



2. Plant in a flowerpot a number of small seeds, such as timothy or radish seed, for comparison with 

 corn and lima beans as to the size and appearance of the plants produced. 



3. Select three potatoes of nearly the same size. Remove all the eyes but one from one of the 

 potatoes. Cut the second into four equal pieces, leaving one eye in each piece. Remove an eye from ' 

 the third potato and leave attached to it a very small piece of potato. Plant these cuttings in sand 

 and compare the rate of growth and the size and vigor of the plants produced. 



Questions. When separated from the rest of the kernel, did the corn germ produce a plant? Did 

 the lima-bean plants live after the seed leaves had been removed ? What are the sources of food 

 used by the young plant in promoting growth? When the material stored in the part planted is 

 exhausted, what happens to the plant growing in sand? If the plants had been growing in a fertile 

 soil, what would have happened when the food stored in the seed was exhausted ? Which will produce 

 the larger and more vigorous plants, large or small seeds, plump or shriveled seeds ? Compare the size 

 of young timothy or radish plants with corn or lima-bean plants. What is the explanation of the 

 differences ? 



References. Waters, H. J. Essentials of Agriculture, pp. 24-26. Ginn and Company. Lyon, Fippin, 

 Buckman. Soils, their Properties and Management, pp. 480-488. The Macmillan Company. Hopkins, C. G. 

 Soil Fertility and Permanent Agriculture, pp. 13-15. Ginn and Company. Bergen and Caldwell. Introduc- 

 tion to Botany, pp. 6-20. Ginn and Company. 



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