SOME PLANT BIOGRAPHIES. 201 



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 rela- 

 tion between the shape and arrangement of the 

 leaves in plants, and the shape and arrangement 

 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 and drains away ; and it is im- 

 portant for each that it should utilise to the ut- 

 most its ow^n particular supply of drainage or rain 

 water. Hence you will find that some plants, like 

 the dock, have large channelled leaves, with a leaf- 

 stalk traversed by a depression like a drainage 

 runnel : plants of this type carry off all the water 

 that falls upon them toward.^ 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, instead 

 of descending straight down, are spreading and 

 diffused, so as to go outward towards the point 

 where the water drips on them. Moreover, in 

 this latter case it is found, on digging up the 

 plant carefully, that the absorbent tips of the 



