seeds? How long can a plant live entirely upon the food that is stored in the seed? Could the young plant start its growth without stored food?

Suggestions for report. Prepare a series of sketches properly labeled illustrating the successive stages of growth of the plant. Reference work. Read sections 379 to 385.

Optional problems. Plant ten or twelve different kinds of seeds, and as they grow determine the nature and variations in the seed leaves of the plants. By the use of a very sharp knife remove the seed leaves from some seedlings as soon as the seed leaves appear above the soil, and determine what effect this has upon the later growth of the young plants.

OVERPRODUCTION OF PLANTS AND ANIMALS (XXXII−1)

The problem. New plants and animals are formed in such large numbers that until one has studied the matter carefully it is difficult for him to believe the facts about the numbers of new individuals that are produced. Any common plant or animal used as the basis of some simple calculations will show the possibilities of production of new individuals.

What to use. Ears of corn, heads of wheat or oats, seed pods of any common plants, data regarding number of eggs laid by a robin or by a toad.

What to do. 1. Determine how rapidly given plants or animals would increase in given lengths of time if all seeds should grow in the case of plants or if all the young of animals should mature. It is suggested that each pupil make but one or two of the calculations and that the results be made available to the entire class.

2. Indian corn. Count the rows and number of grains in a row of one ear. Estimate the number of grains on the ear. Calculate the descendants in the fifth generation, assuming that each grain produces a plant upon which one good ear develops.

3. Wheat. Ascertain the number of grains in a head and suppose that there are five heads to each plant. Calculate the number of grains in the fifth generation.

4. Robin. Assuming that a female robin will lay four eggs (though she may often lay eight in one year) and that one half of the new birds will be females, calculate the number of robins at the end of ten generations if all eggs hatch and no birds die.

5. Toad. A female toad may lay as many as 11,000 eggs in one season. Assuming that 8000 is a fair average and that one 'half the young toads will be females, calculate the number of toads from a single pair at the end of four generations if all eggs hatch and no toads die.

Questions. Do the numbers that you calculate indicate how many might come into existence if all really developed? In what ways do available food, space, light, and proper temperature affect the development of large numbers of new plants or animals? What illustrations in your immediate environment can you cite to show that there is a struggle for existence between the large numbers of new forms that are produced?

Suggestions for report. A summary of the calculations cited above should appear in the notebook.

Reference work. Read Chapter XXXII.

Optional problems. Assuming that an average toad will weigh a quarter of a pound, what would be the weight of the four generations of toads according to your calculation? Why do not plants or animals really increase as rapidly as indicated by the above calculations?

VARIATION IN EARS OF CORN (XXXIII-2)

The problem. In the preceding exercise it became apparent that new individuals are produced in very great numbers. A brief study of these individuals would show that it is very difficult and probably not possible to find any two individuals that are alike. Such a study of ears of corn will prove interesting.

What to use. Enough ears of corn so that each pupil or each two pupils may have one ear as a basis for work.

What to do. 1. Each pupil should calculate the number of grains on one ear. In case grains have been lost, determine how many were lost and add this number to the number counted.

2. Write the total upon the board and also copy in your notebook the totals of all the other pupils. Underline the largest and smallest numbers, and find the average number.

Questions. Can you find two ears of corn that have exactly the same number of grains upon each ear? Do you think you could find any two grains that are exactly alike in every respect?

Suggestions for report. Record the numbers of grains found upon the ears of corn studied by all the members of your class and prepare a graph to show the number of ears having different numbers of grains.

Reference work. Read sections 395 to 400.

Optional problems. Do most of the ears used in the calculations come nearest to the smallest number, to the largest number, or midway between? If you were selecting one ear for planting from all those used in the calculations, which one would you select? What qualities led you to make your selection? Compare the grains and the cobs of the different ears studied. What percentage of the total weight of the ear is the weight of the grains?