SOME PLANT BIOGRAPHIES. 219 



hundreds of them. There is not a tiny hair on 

 the surface of a flower, not a spot or a streak in 

 the blade of a leaf, not a pit or depression on the 

 skin of a seed, that has not its function. And 

 close study of nature rewards us most of all 

 for our trouble in this, that it reveals to us 

 every day some delightful surprise, forces on 

 our attention some hitherto unsuspected but 

 romantic relation of structure and purpose. 



I will mention but one more case as a typical 

 example. There exists as a rule a definite 

 relation between the shape and arrangement of 

 the leaves in plants, and the shape and arrange- 

 ment of the roots and rootlets, with regard to 

 water-supply. Each plant, in point of fact, is 

 like the roof of a house as respects the amount 

 of rain which it catches arid drains away ; and 

 it is important for each that it should utilise to 

 the utmost its own particular supply of drainage 

 or rain water. Hence you will find that some 

 plants, like the dock, have large channeled 

 leaves, with a leaf -stalk traversed by a depres- 

 sion like a drainage runnel : plants of this type 

 carry off all the water that falls upon them 

 towards the centre, inwards. But such plants 

 have always also a descending tap-root, which 

 instantly catches and drinks up the water poured 

 by the drainage system of the leaves towards 

 the middle of the plant. In other plants, again, 

 however, with round leaf-stalks and outward 

 pointed leaves, the water that falls upon the 

 foliage drains outward towards the circum- 

 ference ; and in all such plants the roots, in- 

 stead of descending straight down, are spread- 



