REVIEW AND CONCLUSION 419 



Both require proteid and carbohydrate food, but the 

 green plant is able to manufacture these complex 

 substances itself, utilizing for this purpose the energy 

 of sunlight by means of the chlorophyl contained in 

 its green parts, while animals, behig without this 

 power, are ultimately dependent on plants for their 

 food. It is in the possession of this chlorophyl, essen- 

 tially the same in all assimilating plants, though some- 

 times masked by some special colouring matter, that 

 most plants differ from animals, and this is the explana- 

 tion of the stress laid on colour in the introduction 

 (p. 4). 



When we come to look more closely we find another 

 attribute of living things, adaptation. In a general 

 way every part is wonderfully well adapted for its 

 functions, thus the young parts of the shoot for which 

 the retention of water is important are covered with 

 a waterproof epidermis, while the similar parts of the 

 roots have an absorptive covering of hairs; the axis 

 of shoot and root parts are cylindrical, for their work 

 is to support the leaves and conduct fluids with a 

 minimum of loss, while the leaves whose work is 

 a surface one are flat ; the shoot apex is protected 

 by bud scales, which are usually undeveloped leaves 

 that will afterwards expand and be useful as such, 

 while the end of the root has a protective cap, the 

 wearing away of which as it is pushed through the 

 rough soil, is without appreciable loss to the plant. 



Not only is each part adapted in a general way to 

 its function, but we find special modifications to suit 

 special conditions. The embryo in the seed takes 

 several forms, and its first leaf may be altered almost 



