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plant, e.g. a wheat plant such as is shown in Plate 7, Fig. 

 3, are carefully removed from the soil and examined, their 

 lower portions will be found projecting from a mass of 

 soil particles like naked white threads. Closer inspection shows 

 that these soil particles are clinging to a number of minute 

 hairs which look like very fine shining lines. These are the 

 so-called root-hairs which attach themselves so firmly to the Root-hairs.: 

 soil particles that the latter can only with difficulty, if at all, 

 be separated from them. When looked at with a microscope, 

 each of these hairs is seen to be a tubular outgrowth of a single 

 epidermal cell, into which it opens at the base, with a thin cell 

 wall of cellulose and containing living protoplasm. It is prin- 

 cipally by means of these hairs that roots absorb their 

 necessary supplies of water and substances in solution from 

 the soil, the older parts of the roots taking no part in this work 

 of absorption. If these delicate hairs were formed on the 

 portion of the root which is rapidly elongating they would be 

 rubbed off as the root pushes downwards into the soil, and 

 hence the elongating region is destitute of these hairs. The 

 root -hairs as a rule only live for a few days and then die off, so 

 that they are absent from the older parts of the root, but as 

 new hairs are continually being formed behind the elongating 

 region a zone of active living hairs is constantly maintained 

 there. Owing to the strong adhesion of the root-hairs to the 

 soil particles, the root is firmly held in the soil and the elonga- 

 tion of the area immediately behind the apex must drive the 

 tip of the root down into the soil, as it cannot force up the 

 firmly anchored part of the root behind it. To enable the root 

 to obtain as much water and mineral salts as possible from 

 the soil, it is obviously an advantage for it to have a large ab- 

 sorbing surface which shall come in contact with as many soil 

 particles as possible. Accordingly, the tip of the root as it glows 

 downwards, usually follows an irregular spiral course, and the 

 multitudes of root-hairs give it a very large absorbing surface. 

 The root-hairs having obtained all the supplies they can from 

 the soil within their reach die off, while the lateral roots then 

 tap those layers of soil which were beyond the reach of the 

 hairs of their parent root. 



The upper older portion of the young roots of seedlings Shortening 

 frequently exhibits the peculiar property of contracting, or of Roots - 

 shortening. A pull is thus exercised on both the root and 

 stem, and as the former is strongly anchored the lower portion 

 of the stem is pulled down into the soil and the young plant 

 is thus firmly established. The rooting tips of the branches 

 of Rubus lasiocarpus may thus be seen to be drawn into the 

 ground and similar contraction i often seen in the older roots 



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