RELATIONS OF KOLIAGE-LEAVES To AliSOUBEXT KDin'S. 93 



iucliiuitioii is düwuwards and outwards. Ou their apices great drops are gradualij- 

 formed, which finally detach themselves and fall on to the mass of needles be- 

 longing to a lower branch. Thus transmitted, the rain-water travels through 

 the foliage lower and lower and at the same time further from the axis. This 

 is also the case with larches. The drops of rain which fall upon the erect needles 

 of the tufted " short branches " collect and gradually descend to the needles of 

 the drooping " long branches " on lower boughs. Large drops are always to be 

 seen on their drooj)ing apices, whence they drip to the earth. Owing to the 

 pyramidal form of larches, and to the circumstance that the long shoots on each 

 branch are terminal, almost all the water which falls upon one of these trees 

 reaches the long shoots hanging down from the lowest branches, which discharge 

 most of all. Although larches with their tender needles do not look at all as 

 though they would be any protection against rain, the ground underneath them 

 keeps dry nevertheless, the principal part of the water falling upon them being 

 conducted to the periphery. Indeed, the larch belongs to the number of trees 

 which conduct almost all the rain that falls upon them to a certain distance from 

 the axis where the absorbent roots lie, and only allow a little to trickle down 

 the bark of the main trunk. 



Many shrubs and perennial herbs also transmit the water, which falls on 

 their ujiturued laminae, to parts of the ground where their absorbent roots are 

 embedded; or, rather, the roots send forth their branches bearing absorpti\e cells 

 to the area which is kept moist by drippings from the leaves. Particularly sti-iking 

 in this respect ai-e the species of the two genera of Aroids CoUocasia and 

 Calladium. A specimen of the latter is figured below (fig. 13^). If one digs 

 about imlividuals of this geuvis cultivated on open ground, one invariably finds 

 that the tips of the lateral roots, which proceed in a horizontal direction from 

 the bulbous root-stock, are buried under the point of the great leaves which slope 

 obliquely outwards. We must not omit to mention, in addition, that the stalks 

 of leaves which conduct the rain centrifugally are not channelled on the upper 

 surface; they are round, and comparable to wires supporting at their upper extremities 

 the laminae in an outward and downward direction. As instances we may quote 

 the Horse-chestnut, Maple, and Lime, and many shrubby, suffruticose, and 

 herbaceous plants, such as Sparm.annia, Spircea, Aruncus, and Corydalis, and also 

 climbing and trailing plants (e.g. Menispermum, Bavisteria, Aristolochia, Hoya, 

 Zanonia, and Tropceolum). Whenever a system of grooves is developed on the 

 surface of an outward sloping leaf, the channels run along the veins and terminate 

 at the apex of the leaf, or at the apices of the leaf's lobes, and invariably cause 

 the water to travel, not to the basal part, but to a spot on the mai-gin whence 

 it will detach itself in the form of a drop, and fall upon the leaves situated 

 immediately below and at a greater distance from the axis. 



A striking contrast to these trees and shrubs, climbing and trailing plants, 

 and Rufiruticose and herbaceous species, with their absorptive roots lying in one 

 plane, and usually spreading at but little depth, is aftbrded by plants which possesS' 



