THE TEGETATITE 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 uubranched. 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 abnost 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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