92 RELATIONS OF FOLIAGE-LEAVES TO ABSORBENT ROOTS. 



EELATIOXS OF THE POSITION OF FOLIAGE-LEAVES TO THAT OF 

 ABSORBENT ROOTS 



Anyone who has ever taken refuge from a sudden shower under a tree will 

 remember that the canopy of foliage afforded protection for a considerable time, and 

 that the ground underneath was either not wet at all, or only slightly so. No doubt 

 some of the rain flows down the bark of the trunk, and in many species, as, for 

 instance, the Yew and the Plane-tree, the volume of water conducted down the 

 trunk is considerable; but in the case of most trees the rain-water which reaches 

 the earth in this manner is not abundant, and in comparison with that which drips 

 from the peripheral parts of the foliage its quantity is negligeable. This phenome- 

 non is dependent upon the position of the foliage-leaves relatively to the horizon. 

 In almost all our foliage-trees — in limes and birches, apple and pear trees, planes 

 and maples, ashes, horse-chestnuts, poplars, and alders — these organs slope out- 

 wards, and are so placed one above the other that rain falling upon a leaf on one 

 of the highest branches flows along the slanting surface to the apex, collects there 

 in drops, and then falls on to a lower leaf whose surface is also inclined outwards. 

 Here it coalesces with the water fallen directly upon this leaf; and so it goes from 

 one tier to another, lower and lower, and at the same time further and further 

 from the axis, till a number of little cascades are formed all round the tree. From 

 the under and outermost leaves of the entire mass of foliage the water falls in 

 great drops to the ground, and after every shower of rain the dry area at the 

 foot of the tree is surrounded by a circular zone of very wet earth. It is only 

 necessary to dig at these places to convince one's self that the tree's absorptive roots 

 penetrate the earth precisely to the wet zone. When a tree is j^oung, its roots lie 

 in a small circle, and the crown too is not extensive, so that the damp zone is 

 proportionately restricted. But as the latter is enlarged there is a corresponding 

 elongation of the roots in their search for moisture, and thus roots and foliage 

 progress ^mri passu in peripheral increase. It seems not improbable that the 

 custom amongst gardeners and foresters of trimming the foliage and roots of trees 

 when the latter are transplanted is to be attributed to the phenomenon above 

 described. For the rule is observed that the branches of the trunk and those of the 

 root must be about equally shortened, and accordingly the suction - roots, as they 

 develop, reach the zone of drip of the growing crown. 



A similar method of carrying off water is to be observed in coniferous trees. 

 Take, for example, the Common Pine. The lateral branches are horizontal near 

 the main trunk; the secondary branches curve upwards like bows. The needles | 

 near the tip of each of the latter slant obliquely upwards from the axis, whilst j 

 the older needles, situated on the under side of the part of the branch which is \ 

 almost horizontal and at some distance from its extremity, are directed obliquely i 

 downwards and outwards. Rain-drops striking the upturned needles glide down | 

 them to the bark of the branch in question, and thence to other needles whose ! 



