FUNCTION AND FORM 89 



position as regards the source of light, would 

 be as useless as a heavily shaded one. More- 

 over, with the increase of the leaves the 

 mechanical requirements vitally affect the 

 whole subsidiary apparatus of the plant. The 

 root is concerned in this no less than the stem, 

 for the leaf depends for the proper discharge 

 of its functions on an adequate degree of 

 fixity on the part of the plant as a whole. 



Another factor which materially influences 

 the foliar organs of a plant, lies in the 

 water supply, for if this be deficient or 

 precarious, the leaf area must either be 

 correspondingly reduced, or there must be 

 found some means of checking the loss of 

 water, or else the difficulty must be met in 

 yet other ways. The particular form of solu- 

 tion of the water problem which happens to 

 be adopted by any given plant is a matter 

 that will mainly depend, as already pointed 

 out, on its own inherent constitution. 



It is worth while to endeavour to follow out 

 some of the numerous and diverse ways by 

 which those problems relating especially to 

 mechanical needs and to water supply have 

 been solved by various sorts of plants. Not 

 only shall we encounter remarkable examples 

 of adaptedness to special conditions, but we 

 shall incidentally be brought into close con- 

 tact with some of the more difficult questions 

 of biological philosophy. 



In any event we shall gain a clearer idea 

 of the way in which the whole anatomical 



