GUS3 GA RDEN NA T URE-STUD Y 253 



oxygen in its place. The gas which extinguishes the flame when 

 too abundant, would put out "the vital spark" if not removed. 

 It furnishes food to the plant. (Connect with Hygiene and 

 Sanitation.) 



In past ages much carbon accumulated by plants was made into 

 coal. The heat and other energy which this now furnishes has 

 been called "bottled sunshine. "(Connect with Geography, etc.) 



We eat plants and so get carbon to burn which in turn escapes 

 in our breath. 



In winter the winds bring us pure air from the places where 

 plants are growing for "it's always summer somewhere." (Con- 

 nect with Geography.) 



Discuss other effects of light on plants and the behavior of 

 plants toward light. 



Recall the color of potato sprouts; turning of leaves to the 

 light; why leaves are flat, thin, and broad, usually; shapes and 

 arrangement of leaves with reference to light; how climbing plants 

 seek light. 



References: Atkinson, First Studies of Plant Life, ch. 20, 

 21; Bergen, Elements of Botany, old edition, ch. 10; new, ch. 

 11; Coulter, Plant Relations; Davis, School and Home Garden- 

 ing pp.62, 63, and 64; other Botany and Chemistry text-books. 



