ROOT AND CROWN. 69 



continually reinforced and becomes greater and 

 greater. . . . 



A slightly different method of guiding the rain- 

 water may be seen in the Mullein (Fig. II). 1 The 

 upper leaves, half clasping the stem, are upright, 

 like those of the Alfredia^ and guide the water 

 downward in the same way. But the leaves in 

 the middle portion of the stem are only upright 

 for two- thirds of their length. The upper third is 

 recurved, and the rain which falls on this upper 

 third drops from the points of the leaves, and 

 would thus seem to run off centrifugally. But the 

 shape of the plant is a slender pyramid, as the 

 leaves grow continually smaller towards the top of 

 the stem, and the water drops from the apex of 

 one leaf to the portion of the next lower leaf which 

 slopes inward, and thus leads the water centrip- 

 etally. In this way, the whole of the rainwater 

 falling on such a plant finally reaches the neighbor- 

 hood of the tap-root, and is used to the best ad- 

 vantage by the rootlets proceeding from it. ... 



1 Our species of Mullein, Veibascum thapsus, carries off the rain- 

 water in the same manner. An experimenter has told me that it is 

 necessary to cultivate plants by themselves in order to see this relation 

 in the position of leaves and rootlets, for in the woods and fields so 

 many conditions enter into the result that the growth of the roots may 

 be determined by other causes. ED. 



