ADVANCED Coulter, Barnes, and Cowles, _A Textbook of Botany_, Part II. Amer. Book Co. Duggar, _Plant Physiology_. The Macmillan Company. Goodale, _Physiological Botany_. American Book Company. Green, _Vegetable Physiology_, Chaps. V, VI. J. and A. Churchill. Kerner-Oliver, _Natural History of Plants_. Henry Holt and Company. MacDougal, _Plant Physiology_. Longmans, Green, and Company. VII. PLANT GROWTH AND NUTRITION--PLANTS MAKE FOOD _Problem.--Where, when, and how do 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?_ _(d) 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. (_b_) 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. What becomes of the Water taken in by the Roots?--We have seen that more than pure water has been absorbed through the root hairs into the roots. What becomes of this water and the other substances that have been absorbed? This question may be partly answered by the following experiments. [Illustration: Apple twigs split to show the course of colored water up the stem.] Passage of Fluids up the Stem.--If any young growing shoots (young seedlings of corn or pea, or the older stems of garden balsam, touch-me-not, or sunflower) are placed in red ink (eosin), and left in the sun for a few hours, the red ink will be found to have passed up the stem. If such stems were examined carefully, it would be seen that the colored fluid is confined to collections of woody tubes immediately under the inner bark. Water evidently rises in that part of the stem we call the wood. [Illustration: Experiment to prove that water is given off through the leaves of a green plant.]