THE PLANT AND ITS FOOD 27 



when it will withstand complete desiccation. 

 When it is grown in water containing traces of 

 available nitrogenous food it is green, thrives, 

 and multiplies rapidly, but if the supply 

 of nitrogenous food is used up, the rate of 

 increase drops, and the plants change colour, 

 owing to the degradation of the chlorophyll 

 and the corresponding development of a 

 reddish pigment. When it has reached this 

 condition the addition to the water of a small 

 supply of nitrogenous food, such as a crushed 

 fly, rapidly brings about the restoration of 

 the green colour in the cells. When found 

 growing on snow-slopes, the red tint is 

 obviously due to the absence of available 

 nitrogenous food, possibly coupled with the 

 conditions of intense illumination and low 

 temperature prevailing in such situations, for 

 when the plant is once more suitably nourished 

 the green colour soon re-appears. 



To sum up, then, what we have learned of* 

 the significance of chlorophyll, both to the 

 plant and to the world at large, we may say 

 that its primary function is to enable its 

 possessor to synthesise important complex 

 foodstuffs from very simple raw materials; 

 in other words, that a part of the energy 

 contained in the sunlight is rendered available 

 for the use of the plant. Furthermore, that 

 the sugars or their representatives thus 

 formed, provide the starting-point for still 

 other reactions which go on within the body. 

 They more directly supply the energy which 



