PLANT PHYSIOLOGY 15 



future use, is stored within the plant (as starch in 

 tubers, etc.) : — 



(8) C6HiA-H,0 = CcH,o05. 



Prof. S. H. Vines has conclusively proved that 

 there is a starch- changing, or diastatic, ferment 

 (enzyme) in all green leaves. 



Light is essential for assimilation,^ and also iron. 

 ' ' Plants grown in solutions devoid of iron produce 

 at first normal green leaves. Very soon, however, 

 they begin to appear sickly ; in fact when the 

 iron in the seed has been used up, they become 

 icteric and chlorotic. The new leaves are no 

 longer green, but white, and a microscopic 

 examination of them shows that abnormal chloro- 

 phyll bodies, or none at all, are present in the 

 cells. If we add to the food solution a few drops 

 of ferric chloride solution, the previously white 

 leaves become green in two or three days, and the 

 growth of the plant now proceeds normally." In 

 the words of Boussingault, " le fer parait tout 

 aussi indispensable k la vie v^g^tale qu'k la vie 

 animale." 



' Everyone has noticed how the leaflets of the clover change 

 their position as the light of day wanes ; they are expanded during 

 the day, and folded downwards in the evening. There are similar 

 movements in mimosa, acacia and other plants. Linnseus called ij; 

 the somnus plcmtarum — the sleep of plants. 



