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ROOT-HAIR

1633

ROSE

duced a Te Deum and other more pretentious pieces. He received the doctorate from Chicago University in 1892. He died on Aug. 6, 1895.

Root-Hair. See ROOT.

Root=Pressure. When plants have their roots in a warm soil and the parts in air are not losing much water (whether because the leaves are not yet formed or because the moisture or coolness of the air do not permit evaporation), the roots may absorb water so rapidly (see ABSORPTION) that it distends the cells and escapes into the conducting tissues under the elastic pressure of the stretched cell-walls. (See TURGOR.) By this pressure it may be driven through the conducting tissues to some distance above the ground, and may well out at a wound. Late-pruned grape-vines "bleed" in this way, and much of the so-called dew on a lawn is water which has exuded from the leaves on account of root-pressure. Many leaves have special openings (water-pores) which permit the escape of water at times. But when evaporation is rapid, root-pressure falls to zero or becomes negative; while, therefore, it may assist in supplying water to leaves, it fails when the need is the greatest, and cannot be an important agent in the ascent of water. See WATER, ASCENT OP.

Root'stock', an underground stem, usually horizontal and much thickened by the storage of reserve food. That the structure is a stem may be recognized by the fact that it often bears reduced leaves. It really is the primary shoot of the plant, and sends out its branches or leaves above ground. An equivalent word is rhizome.

Root=Tubercles (tu'bfr-k'ls). On the roots of many leguminous plants, as the clovers, little wart-like outgrowths frequently occur, known as root-tubercles. It is evident that these are occupied by bacteria, which swarm in them and doubtless obtain food from the roots of the host. These bacteria have the peculiar power of laying hold of the free nitrogen of the air circulating in the soil and of supplying it to the plant in some usable form. This habit of clover and its allies explains why they are useful in what is called restoring soil. After ordinary crops have exhausted the soil of its usable nitrogen salts and it has become relatively sterile, clover is able to grow by obtaining nitrogen from the air by the root-tubercles. If the crop of clover be plowed under, the nitrogenous material thus organized is contributed to the soil, which is thus restored to a condition which will support the ordinary crops again.

Ropes are usually made of vegetable fibers, and differ from twine only in their greater thickness. The fiber in most constant use is hemp, though ropes are also made of manilla or wild plantain and of wire. Coir fiber from the husk of the cocoanut is another important rope-making material, which has

the advantage of being lighter than either hemp or manilla. Sisal hemp from South America is also used to a considerable extent, especially for ropes of small size, and for many purposes cotton-ropes are also employed. Notwithstanding the extensive use of machinery in the manufacture of ropes, the old process of rope-walk spinning is still practiced on a considerable scale. The successive stages in this process are (i) hackling the fiber; (2) spinning the yarn; (3) tarring in ''hauls/' consisting of about 300 yarns; (4), winding the yarn on bobbins and mounting these on bobbin-frames; (5) forming the strands; and (6) laying the strands into a rope. As life and property depend to so great an extent on the efficiency of ropes, great care and ingenuity have been exercised in the manufacture, causing many improvements to be devised for increasing their strength. Among these is the introduction of wire-ropes, which are extensively used in rigging ships and for other purposes These are generally made of iron wire, sometimes but not always galvanized. The twisting is done in the same way in which the strands of a hempen rope are laid together.

Rose. The well-known name of the genus Rosa and the type of a great family of plants.

THE  AMERICAN-BEAUTY  ROSE

It is one of the most prized of the cultivated ornamental forms, and is distributed over the whole temperate and subalpine region of the northern hemisphere. Over 200 species have been described, only about 15 or 20 of which occur native to North America. The varieties in cultivation are almost innumerable, both those which are hardy and those adapted for culture under glass.

The great beauty of the rose, its fragrance and its color have made it perhaps the most popular of all flowers, and yet it is