RELATIONS OF FOLIAGE-LEAVES TO ABSORBENT ROOTS. 



97 



of the stem are only erect for about three-quarters of their length; the upper- 

 most third, including the apes, is bent obliquely outwards and downwards. Drops 

 of rain falling on this upper third of a leaf would flow in a centrifugal direction, 

 and do, as a matter of fact, drip down from the apex. Xow the leaves in all 



Fig 14 — Irrigation of Rain-water. 

 1 In Al/redia cernua. 2 In a Mullein ( Verbascum pklomoides). 



these plants are shorter the higher their position upon the stem, so that the total 

 contour of the plant may be described as a slender pyramid. In consequence of 

 this, water dropping from the outward-bent and drooping apices of superior leaves 

 is arrested by that part of an inferior leaf which shelves towards the stem, and is 

 thereby conducted centripetally. Thus all the rain-water received by a plant 

 of this kind at last reaches the immediate neighbourhood of the tap-root, and is 



Vol. I. 7 



