VII. PLANT GROWTH AND NUTRITION — PLANTS 

 MAKE FOOD 



Problem. — Where, when, and how green plants make food. 



(a) How and why is moisture given off from leaves ? 



(b) What is the reaction of leaves to light ? 



(c) What is made in green leaves in the sunlight ? 



id) What by-products are given off in the above process ? 

 (e) Other functions of leaves. 



Laboratory Suggestions 



Demonstration. — Water given off by plant in sunlight. Loss of weight 

 due to transpiration measured. 

 Laboratory exercise. — 



(a) Gross structure of a leaf. 



(6) Study of stoma and lower epidermis under microscope. 



(c) Study of cross section to show cells and air spaces. 

 Demonstration. — Reaction of leaves to light. 

 Demonstration. — Light necessary to starch making. 

 Demonstration. — Air necessary to starch making. 

 Demonstration. — Oxygen a by-product of starch making. 



To the Teacher. — In this chapter experimental work may be made to carry 

 almost the entire plan of the chapter. That plants make food out of raw food 

 materials may be demonstrated by a series of logical experiments which leave no 

 doubt as to the steps taken or the factors involved in this wonderful process. That 

 the whole world depends upon the process of photosynthesis is well known. A 

 concept of what the process is and what it does for mankind should be known by 

 every pupil when he has finished the exercises which follow. Laboratory problems 

 having rigid adherence to the logical sequence of events which culminate in food 

 making and food storage in the leaf, will result in increased power on the part of 

 the pupil and a beginning of appreciation of what a developed problem really 

 means. To the critic who would object to so much time given to the processes 

 involved in photosynthesis, we would say : starch making and food making may 

 be tied up in a vital manner to the interest of the city child by drawing atten- 

 tion to the economic importance of cereal and other staples furnished man by 

 plants, and by making clear the tremendous importance of green plants in the role 

 of food makers on the earth. (See Chapter XI, Civic Biology.) 



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