Ctiltural First Principles. 605 



alone concerned, generally branches considerably, its minor ramifica- 

 tions being known as rootlets. 



The root serves a threefold pm'jjose. It fixes the plant, it absorbs 

 nutriment, and in many cases it stores it for future use. 



I need only illustrate the first function by mentioning that in 

 nursery gardens the tap-root of apple, peach, and other trees is 

 removed when they are young to facilitate transplanting. On the 

 other hand, the untouched roots of the ash have been known to reach 

 a length of ninety-five feet ; and I thin]^: I can testify to those of the 

 Lombardy poplar attaining an equal length. 



The ahsorptioii of food from the soil is the most important function 

 of the root. This function is performed by the whole surface of the 

 root, which is still young and unhardened in texture ; but more 

 especially by myriads of microscopic hairs, with which the rootlets of 

 most trees are covered. 



The silver fir {Abies picea) has no root-hairs, but a delicate, highly 

 absorbent cuticle or surface-layer, with very numerous rootlets. Old 

 roots acquire a corlcy rind which renders them impervious, the func- 

 tion of absorption being then transferred to the rootlets. 



The soil has great influence on the extension of roots, they being 

 thicker and numerously branched in rich, and attenuated and with 

 but few rootlets in poor soils. 



It appears at first as if roots went in search of food, the real fact 

 being that they can only grow in those directions in which they find 

 food. They send out rootlets in all directions, but those which find 

 no nourishment remain no further developed. 



The cells of the rootlets and their .prolongations, the root-hairs, 

 take up liquids from the soil in the same manner that in the plant 

 liquids pass from one cell to another, that is by the physical process 

 known as " osmose," each root-hair being closely applied to a particle 

 of soil, and the moisture in the soil coating its constituent particles. 

 One of the substances roots give out in this process is carbonic acid, 

 which acts as a solvent on carbonate of lime. This was proved by 

 Sachs, who sowed seeds in sand on polished plates of marble (calcium 

 carbonate), dolomite (calcium-magnesium carbonate), and osteolite 

 (calcium phosphate), and found that an impression of the root-system 

 was etched or eroded into the stone. 



The stem, though not usually contributing to the nutrition of the 

 plant, is, of course, of paramount importance to the forester. It is 

 the medium by which the food-substances are conveyed from the 

 roots, and also partly the laboratory of physiological change and the 

 storehouse of the plant, as well as the framework which spreads out 

 the leaves or manifold stomach and lungs of the plant into that im- 

 portant food-supplying medium, the air. The stem originates in a 

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