96 PLANTS MAKE FOOD 



Respiration by Leaves. — All living things require oxygen. It 

 is by means of the oxidation of food materials within the plant's 

 body that the energy used in growth and movement is released. 

 A plant takes in oxygen largely through the stomata of the leaves, 

 to a less extent through the lenticels or breathing holes in the stem, 

 and through the roots. Thus rapidly growing tissues receive the 

 oxygen necessary for them to perform their work. The products 

 of oxidation in the form of carbon dioxide are also passed off 

 through these same organs. It can be shown by experiment that 

 a plant uses up oxygen in the darkness ; in the light the amount 

 of oxygen given off as a by-product in the process of starch-making 

 is, of course, much greater than the amount used by the plant. 



Summary. — From the above paragraphs it is seen that a leaf 

 performs the following functions : (1) breathing, or the taking in 

 of oxygen and passing off of carbon dioxide ; (2) starch-making, 

 with the incidental passing out of oxygen ; (3) formation of proteins, 

 with their digestion and assimilation to form new tissues; and 

 (4) the transpiration of water. 



Reference Books 



elementary 



Hunter, Laboratory Problems in Civic Biology. American Book Company. 

 Andrews, A Practical Course in Botany, pages 160-177. American Book Company. 

 Coulter, A Textbook of Botany, pages 5-40. D. Appleton and Company. 

 Covilter, Plant Life and Plant Uses. American Book Company. 

 Dana, Plants and their Children, pages 135-185. American Book Company. 

 Sharpe, A Laboratory Manual in Biology, pages 90-102. American Book Company. 

 Stevens, Introduction to Botany, pages 81-99. D. C. Heath and Company. 



ADVANCED 



Clement, Plant Physiology and Ecology. Henry Holt and Company. 



Coulter, Barnes, and Cowles, A Textbook of Botany, Part II, and Vol. II. American 



Book Company. 

 Darwin, Insectivorous Plants. D. Appleton and Company. 

 Duggar, Plant Physiology. The Mj*cmillan Company. 

 Goodale, Physiological Botany, pages 337-353 and 409^24. American Book 



Company. 

 Green, Vegetable Physiology. J. and A. Churchill. 



Lubbock, Flowers, Fruits, and Leaves, last part. The Macmillan Company. 

 MacDougal, Practical Textbook of Plant Physiology. Longmans, Green, and 



Company. 

 Report of the Division of Forestry, U. S. Department of Agricultuie, 1899. 

 Ward, The Oak. D. Appleton and Company. 



