64 KOOT AND CKOWN. 



been cultivated in open ground, be dug up, the 

 ends of the roots, which run out horizontally from 

 the stubby rootstock, will be found embedded di- 

 rectly under the points of the large leaves. 



It must not remain unnoticed that the petioles 

 of leaves which lead the rainwater centrifugally, 

 as the leaves of Horse-chestnut and Maple, of shrubs 

 like the Lilac, and of climbing plants like the Tro- 

 paeolum, 1 are not channelled on the upper side, but 

 are round and smooth. If a sloping leaf shows a 

 system of channels for the water, these channels 

 run along the veins and end at the apex of the 

 leaves, or at the points of the lobes. There the 

 water collects in the form of drops, and must fall 

 on the leaves which make the succeeding lower 

 and outer steps. 



In striking contrast to these plants, with leaves 

 sloping outwards and roots spreading horizontally, 

 are those with bulbs or short rootstocks and de- 

 scending rootlets. This contrast in the growth of 

 the root is shown in Fig. 10, 1 and 2. Above the 

 ground it is foretold by the form and position of the 

 leaves on which the rainwater strikes. In all these 

 plants the leaf surfaces slope towards the axis. 



1 When several examples of plants, illustrating a single point, are 

 given, the liberty has been taken of choosing those only which are well- 

 known in America. ED. 



