260 THE YEAR-BOOK OF AGRICULTURE. 



wants.' The larger sheets, such as those used by the Canton flower-painters, are sold for 

 about l\d. each. 



" If the Tung-tsaou proves hardy in England, its fine foliage will render it a favorite among 

 ornamental plants in our gardens." 



Healthiness of the Roots of Plants Essential to their Successful Growth, 



THE following, from the Floricultural Cabinet, is a valuable contribution giyen upon the 

 authority of the most distinguished physiological botanists, and doubtless represent! the 

 truth, at least in part, in regard to the absorbent powers of roots, and the ascent of sap in 

 plants. The objection in regard to mulching would hold good where rich, warm manures 

 are used, such as horse-dung ; but not so where straw, leaves, salt-hay, or other rough refuse 

 material are employed. Ed. Working Farmer. 



As the roots of plants are the chief medium through which they receive nourishment, 

 some account of their structure, and of the curious and simple mode by which they effect 

 their object, will, I hope, prove of some utility to the readers hereof. 



The root may be defined to be that portion of a plant which grows in an opposite direc- 

 tion to the stem, and differing from the latter in its remarkable downward tendency and 

 from its disposition to shun the light of day. So powerful, indeed, is this disposition to 

 descend, "that no known force is sufficient to overcome it." The chief object of the root 

 appears to be that of fixing the plant firmly in the earth, and of taking up a supply of moist- 

 ure from the humid medium by which it is surrounded. It usually consists of several rami- 

 fications, from the sides and extremities of which, without apparent order or regularity, 

 proceed an indefinite number of delicate fibrils with spongy points. N9W these fibrils are 

 the only true roots, and to their soft extremities (spongelets) is consigned the whole office 

 of absorbing fluid ; the more woody portion of the root merely serving as canals to convey 

 the fluid thus obtained to the upper part of the plant. The roots generally pierce the soil in 

 a downward or horizontal direction, according to the individual habit, but more especially in 

 that course which offers the least resistance and yields the greatest quantity of soluble food. 

 Hence the propriety of mulching is, by some gardeners, called into question, because the 

 richness of the mulching material, and the warmth produced by its fermentation, has a ten- 

 dency to attract to the surface the young fibrils. And then, upon the removal of the manure 

 employed in the operation, their extremely succulent and tender tips become exposed to the 

 influence of drought, &c., than which nothing can be more injurious, as it quickly destroys 

 their absorbing power, and thus deprives the plant of its chief source of nourishment. It 

 has been said that the fibrils are the only true roots, and that the feeding function is chiefly 

 confined to the lax tissue of their extreme points. That, this is really the case there can be 

 no reasonable cause to doubt, or why should the success of planting depend so materially 

 upon their preservation ? it being a well-known fact that subjects of any size, such as fruit- 

 trees, are invariably less prolific the first season after transplantation, than on the previous 

 and ensuing years. Why these little spongelets should possess the power of absorbing moist- 

 ure with great force, and of transmitting it to every part of the plant, is a curious question, 

 and has given rise to many ingenious conjectures. But it has at length been satisfactorily 

 answered by that clever French author, M. Dutrocet. If a small glass-tube, having its end 

 covered with a piece of bladder, be partially filled with gum-water, and then plunged into 

 simple water, sufficient to wet the outside of the bladder, the latter will be permeated by the 

 water, and the volume within the tube will continue to increase, so long as the density of the 

 fluids on each side of the intervening membrane remains unequal. " But there is also a con- 

 trary current to less amount the interior fluid passing out to mix with the surrounding 

 water." The first and more powerful of these currents is called endosmose, (flow inwards,) 

 and the second and less powerful, exosmose, (flow outwards.) The cause of their motion 

 was by Dutrocet referred to galvanism ; but it is now more generally believed to arise from 

 "the attraction exerted between the particles of the different fluids employed, as they meet 

 in the porous membrane." Dr. Reid. 



" Now the conditions requisite for this action are two fluids of different densities, separated 



