LEAF ADJUSTMENT 



S3 



direct. Seeds germinate, bulbs and rootstocks perform 

 their vegetative functions, and many parasites and sapro- 

 phytes grow and flourish in the dark, but in these cases it 

 is always at the expense of reserve material provided by 

 the plant itself, or by the host, through the agency of 

 chlorophyll acting in the light. ^ It is the green leaves of 

 summer that lay up the stores of food in bulbs and root- 

 stocks for winter, and 

 flowering stems will even 

 grow and blossom in the 

 dark if enough green 

 leaves are left exposed 

 to manufacture nourish- 

 ment for them. 



Pass the end of a 

 budding flower stem of 

 any gteen-leaved plant — 

 gourd, squash, water 

 melon, morning-glory, 

 etc., make good examples 

 — through a small hole 

 into a dark box, leaving 

 the rest of the plant ex- 

 posed to light, and taking care not to bruise or injure it in 

 any way. Cover the entire leafy portion of another plant 

 of the same kind with a box, leaving only the flower bud 

 exposed, and covering, or cutting away any new leaves 

 that may appear. Watch what happens, and at the end 

 of two or three weeks compare results. The green plant 

 may not show any change for several weeks, until it 

 has used up the chlorophyll already stored away in its 

 leaves. 



Experiments like the foregoing show very plainly that 

 it is no mere figure of rhetoric to speak of the coal hidden 

 away in the earth as " stored up sunshine." 



1 Recent discoveries have given reason to believe that a few of the bacteria 

 are exceptions to this statement, but with regard to the generality of plants, it 

 holds true. 



105. — Experiment with a gourd developed 

 partly in the dark and partly in the light. 



