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14 
ABSORPTION IN PLANTS. The process by 
which plants take in their nourishment. As a 
plant has no one organ similar to the mouth of 
an animal, it might seem to a superficial observer 
to be incapable of receiving nourishment, and 
was formerly regarded by even botanists as nour- 
ished by methods which were comprehensible 
only in theory, and could not be subjected to the 
test of observation. Yet leaves and flowers have 
always been observed to be refreshed by the ac- 
cess of air and moisture, and must, in conse- 
quence, be nourished by means of inhaling and 
absorbing; and entire plants have always been 
known to grow and accumulate substance when 
' rooted in the soil, and, in consequence, must be 
nourished by some process of feeding through 
the roots. The total want of any individual organ 
_ of the nature of a mouth, simply evinces that all 
vegetable nourishment must be obtained in the 
form of gas or liquid, and received or drunk up 
through numerous minute stomata or pores. 
The epidermis or outer bark of plants was de- 
scribed by some of the earlier vegetable physiolo- 
_ gists as of so compact a texture, that no eye, even 
when aided by the best microscopes, could dis- 
cover in it any pore or aperture ; yet it was clearly 
discovered by the celebrated naturalists, Hedwig 
_and De Candolle, to abound in pores; and it dis- 
closes its profusely porous character to the most 
common observer who uses a microscope of suffi- 
cient power. If a plant of any species of moss, 
so far dried as to have shrunk or shrivelled, be 
immersed in water, it will immediately begin to 
imbibe moisture, and will speedily reacquire its 
original plumpness and verdure ; and it obviously 
receives the aliment which revives it, only through 
the medium of the pores of its epidermis. 
If the'bulb of a hyacinth be placed in such a 
manner upon a glass vessel nearly filled with 
water that only the lower parts of the radical 
fibres shall be immersed, it sends up the elements 
of a stem, or very evidently begins to grow, and, 
| at the same time, occasions a perceptible diminu- 
tion in the volume of the water; so that it ob- 
viously absorbs liquid through minute tubes of 
the radical fibres, and elaborates this into the in- 
crease of substance which constitutes its growth. 
All roots terminate in a greater or less number, 
‘most of them in a great multitude, and many of 
them in literal myriads, of minute, absorbing, 
drinking, spongioles, or spongelets, situated at 
the ends of fine, filiform, terminal, radical fibres. 
These countless and microscopically small organs 
are pulpy and bibulous, and bear the name of 
spongioles or spongelets, in consequence of their 
drinking up moisture from the soil as if they 
were little sponges. They consist severally of one 
or more central ducts or vessels, enveloped by a 
cellular tissue, but without any epidermis; and 
they constitute the grand apparatus by which 
plants obtain from the soil, and from its aerial, 
saline, and aqueous accompaniments, the chief 
materials of their growth and substance. A 
ABSORPTION IN PLANTS. 
knowledge of their existence, and of the nature | 
and importance of their functions, explains the 
reason of the scientific gardener’s care to pre- 
serve the extremities and minutest fibres of the | 
roots of any choice plants which he is transplant- 
ing ; it explains also the advantageousness of lift- 
ing, with as full a ball of adhering soil as possible, 
all such garden plants as are designed to be potted, 
transported to a distance, or otherwise kept alive ; 
it shows also why damage is inflicted upon a 
transplanted shrub or tree by cutting away a con- | 
siderable portion of its roots, or by not assigning 
it in its new position a soft wide bed for the easy, 
rapid, and extensive formation of new radicles 
and spongioles ; and, to every gardener and farmer 
of ordinary reflection, it will suggest a crowd of 
valuable hints as to the most beneficial method 
of conducting hoeing, transplanting, and all other 
operations which affect the roots of plants. 
The spongioles, it must be understood, are not 
distributed over the whole of a plant’s roots, but 
are situated only at the extremities of the small, 
hairy radicles or fibres. All such portions of a 
root as possess an epidermis, or have acquired a 
certain degree of consistency, are destitute of 
spongioles; yet all the roots and rootlets fairly 
beneath the soil are continually lengthening and 
ramifying,—and, in the whole of their growth, 
they provide and almost clothe themselves with 
new series of the filiform radicles, which termi- 
nate in spongioles. Various experiments were in- 
stituted by Hales, to show the absorbing power 
of roots, and the force with which it acts; but as 
they were made chiefly on the sections of roots 
laid bare and immersed in water, they afforded 
no direct illustration of the natural action of the 
spongioles,—collecting nourishment at ten thou- 
sand different points, appropriating it with a 
nicety resembling instinct, and drinking it up in | 
a manner and with a power akin to animal vital- 
ity. The power which the spongioles possess and — 
exercise, in drawing liquid from the soil and 
pumping it into the interior of trees or of other 
plants, cannot be very accurately calculated ; yet 
it has been ascertained with sufficient approxi- 
mation to be distinctly understood, and to be 
made the subject of comparison; and, when the 
minuteness of the spongioles is taken into ac- 
count, this power must be pronounced perfectly 
stupendous, and is seen to resolve itself, not into 
any mechanical principle, no matter how magni- 
ficent, but into the mysterious and indefinable 
principle of life. 
. The action of the spongioles, however, is far 
from being uniform in different descriptions of 
impregnated soil or liquid, but is materially mo- 
dified by the mechanical character of the ingre- 
dients which it holds in solution. If a plant be 
placed in water, mixed with gum, sugar, or any 
other similarly viscous substance, it will absorb 
a larger proportion of the water itself than of the 
accompanying ingredient; if placed in water, 
mixed with any substance which does not sen- 
