94 



RELATIONS OF FOLIAGE-LEAVES TO ABSORBENT ROOTS. 



bulbs or short root-stocks with deep-reaching suction-roots, and those wliich liave 

 tap-roots descending vertically in continuation of the main stem, and whose second- 

 ary roots are short and travel only a little distance from their places of origin. 

 This other extreme in root-structure, which is represented in fig. 13-, has its 

 counterpart above-ground in the form and dii'ection of the laminae upon which 

 the rain falls. In all these plants the surfaces of the leaves are not directed 



^"IJ-. 



■^^ 



fij --■ 



Fig. 13. — Centrifugal and Centripetal Transmission of Water. 

 I By a Calladiutit. 2 By a Rhubarb plant. 



outwards, but slope obliquely towards the central axis. Their upper sides, more- 

 over, are concave and exhibit a system of grooves, which conveys the M-ater collected 

 by the leaf towards the stem, and therefore also, towards the tap-root and suction- 

 roots. The leaves of bulbous plants, such as the Hyacinth and Tulip, all stand 

 up oblifjuely, and their upper surfaces are concave and often deeply' channelled. 

 Along the grooves the rain flows centripetally downwards, and so directly reaches 

 the pai-t of the earth where the bulbs and suction-roots, which proceed in a tuft 

 from underneath the bulbs, are situated. The young leaves of Cannacese and of the 

 Lily-of-the-valley are coiled up like a trumpet; aud rain, falling from above 

 upon the expanded portion, is led along the coiled surface, describing a helix as 



