4 PLANT PHYSIOLOGY 



grounds of practical growers of plants ; and there is well-nigh uni- 

 versal belief that great results are to be expected in this direction 

 in the future. Whether for one, several, or all of these reasons, 

 every educational institution aiming to put its students into touch 

 with contemporary progress has established, or must establish, 

 competent instruction in Plant Physiology. And the subject 

 will rise still higher in general estimation as it advances to a loftier 

 plane of scientific efficiency. 



It is fitting, now, to consider the place the subject should 

 have in the educational curriculum. 



In an ideal plan of study the student would first come 

 into contact with Plant Physiology, though not by that name, 

 in his nature study in the lower schools. Here he should learn, 

 along with the salient facts about the common plants around 

 him, and simply as fact, without regard to method or system, 

 those great physiological truths which mean so much for an 

 understanding of the circumambient world, such as these: 



That roots absorb water and minerals and pass them up to the stems. 



That stems conduct water with dissolved minerals from roots to leaves, 

 where the water is evaporated, and that they spread the leaves out into 

 the light. 



That green leaves in light absorb carbon dioxide from the air, and, com- 

 bining this with water and minerals from the soil, manufacture their 

 food, which food nourishes not only them, but also all animals. 



That all living plants need oxygen precisely as animals do, and, like them, 

 give off carbon dioxide, and it is only in green leaves in light, that a 

 reverse process also occurs. 



That the growth of plants is promoted by warmth, ample oxygen, suffi- 

 cient moisture, and, sometimes, by darkness. 



That growing parts have the power to turn towards, across, or away from 

 light, water, or the up-and-down direction according as may be best 

 for the performance of the functions of the parts. 



The experimenting should be all of the simplest sort, with, 

 apparatus put together by the pupil himself; for the child is 

 very self -centered, and can best be taught through appeal to 

 his self-importance. Later in this book, under the appropriate 

 topics, and usually in connection with "make-shift" apparatus, 

 I give such suggestions as I can upon this teaching. 



The student should next meet with the subject in his ele- 



