THE VEGETATIVE ORGANS OF PLANTS. 241 
the vessels were placed in water until the earth was soft- 
ened, so that by gentle agitation it could be completely 
removed from the roots. The latter, on being suspended 
in a glass vessel of water, assumed nearly the position they 
had occupied in the soil, and it was observed that where 
the fertilizer had been thoroughly mixed with the soil, 
the roots uniformly occupied its entire mass. 
Where the fertilizer had been placed in a horizontal 
layer at the depth of about one inch, the roots at that 
depth formed a mat of the finest fibers. Where the fer- 
tilizer was situated in a horizontal layer at half the depth 
of the vessel, just there the root-system was spheroidally 
expanded. In the cylinders where the fertilizer formed a 
vertical layer on the interior walls, the external roots were 
developed in numberless ramifications, while the interior 
roots were comparatively unbranched. In pots, where 
the fertilizer was disposed as a central vertical core, the 
inner roots were far more greatly developed than the outer 
ones. Finally, in a vessel where the fertilizer was placed 
in a horizontal layer at the bottom, the roots extended 
through the soil, as attenuated and slightly branched 
fibers, until they came in contact with the lower stratum, 
where they greatly increased and ramified. In all cases, 
the principal development of the roots occurred in the 
immediate vicinity of the material which could furnish 
them with nutriment. 
It has often been observed that a plant whose aerial 
branches are symmetrically disposed about its stem, has 
the larger share of its roots on one side, and again we find 
roots which are thick with rootlets on one side, and nearly 
devoid of them on the other. 
Apparent Search for Food.—It would almost appear, 
on superficial consideration, that roots are endowed with a 
kind of intelligent instinct, for they seem to go in search 
of nutriment. 
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