HOW THE PLANT LIVES 



129 



gas will be seen to rise and collect in the tube. If a sufficient 

 quantity of this gas could be quickly collected, on testing it 

 with a lighted taper the flame would be seen to quicken per- 



K. 42 Opening of 

 a buu of pear. 



Fig. -i:!. The marking of the stein and 

 the spreading apart of the marks. 



ceptibly, indicating more oxygen than is contained in the air. 

 In this case the carbon dioxid used is in solution in the water. 

 The Elodea is common in still ponds. 



20la. On the subject of temperature and plant life, compare 

 Bailey, "The Survival of the Unlike," pp. 44-48, Chapters xvii. 

 and xix. ; and Chapter xiii. of Gaye's" Great World's Farm." 



202a. Compare Arthur and MacDougal, " Living Plants and 

 their Properties," pp. 85-98, for a discussion of the influence of 

 cold in injuring plants. 



203a. To tst for starch in a potato tuber or other storage 



