Page:Collier's New Encyclopedia v. 03.djvu/478

LEFT DRAGON MOUNTAINS 416 DRAINAGE DRAGON MOUNTAINS. See DrakeN- BERGE. DRAGON'S BLOOD, in botany a wing- leaved, slender-stemmed palm, similar in habit to that which furnishes the chair canes. It is a native of Sumatra and other Malayan islands. The fruits, which grow in bunches, are about the size of a cherry, and are covered with imbricating scales of a red color, coated with a resinous substance, which is col- lected by placing the fruits in a bag and shaking them; the friction loosens the resin, which is then formed into sticks or cakes, and constitutes the best drag- on's blood of commerce. In commerce, sanguis draconis, a resin, so called on account of its red color. It exudes from various trees, either spontaneously or from incisions. There are three kinds in commerce: (1) East Indian dragon's-blood, which is found on the ripe fruits and leaves of several palms of the genus Calamus — viz., C. rotang, C. draco and C. Petroeus; (2) American, obtained from incisions in Pterocarpus draco, indigenous to the West Indies; and (3) Canary dragon's- blood from Dracoena draco. Dragon's- blood is dark-red brown, opaque, taste- less, scentless, and brittle. When pure it dissolves with a fine red color in al- cohol and in ether, and in oils both fixed and volatile; alkalies also dissolve it more or less completely. Nitric acid oxidizes dragon's-blood, forming oxalic acid, but dilute nitric acid heated with the resin, yields nitrobenzoic acid. Drag- on's-blood is used for coloring varnishes, for preparing gold lacquers, for tooth tinctures, and for giving a fine red color to marble. D R A G N'S HEAD, a genus of Labiatx, common in gardens, so called from the form of its corolla. DRAGON'S MOUTH, a popular name for antirrhinum, generally replaced in common usage by that of snap-dragon. DRAGON TREE. See Drac^na. DRAGOON, a kind of mounted soldier, so called originally from his musket (dragon) having on the muzzle of it the head of a dragon. At one time dragoons served both as mounted and foot sol- diers, but now only as the foi'mer. In the British army there are heavy and light dragoons. The first dragoon regi- ment, the Scots Greys, was formed in 1681. DRAGOON BIRD, same as umbrella bird. DRAINAGE, a process by which wet and unhealthy soils are rendered arable and healthy. Benefits of Drainage. — 1. Removal of superfluous water. Not only is the standing water at the surface carried off, but the water-table is lowered, in- creasing the depth of soil. 2. Improves soil texture. Drained soils are more friable, less lumpy, offer less resistance to plant roots, and are of better texture in every way, than un- drained soils. 3. Increases root pasturage. Agricul- tural literature is full of testimony to the benefits of deep tillage. The deeper the soil is stirred the greater its produc- tiveness. 4. Increases soil fertility. It prevents loss of fertility by water passing over the surface. It adds to the fertility by send- ing summer showers down through the soil, instead of over them, enabling the crop to use the nitric acid and ammonia brought down. It increases the effect of manures by bringing them more quickly into solution and into more intimate con- tact with plant roots. 5. Makes tillage easier. Waste land is reduced, and the better texture of soil, its finer tilth and greater friability decrease draft and increase the effectiveness of tillage implements. 6. Lengthens the g^rowing season for crops. Frost comes out earlier in the spring and the land becomes earlier warmed. Evaporation lowers tempera- ture, but drainage removes water without evaporation. 7. Assists disintegration. Frosts pene- trate deeper in winter in drained soils, as- sisting in unlocking the stores of mineral plant food. 8. Favors nitrification and bacterial ac- tion. Plants are largely dependent on the decomposition of organic matter in the soil for their supply of nitrogen. This change is brought about by the action of ferments or bacteria which thrive only under certain conditions of temperature and moisture. Drainage supplies the most favorable condition for their develop- ment. 9. Prevents heaving. The effect of stool-ice in throwing out young plants in winter is often to diminish seriously and even destroy the crop. Drainage dries up the surface soil and prevents the for- mation of stool-ice. 10. Lessens washing and diminishes violence of floods. By increasing the ab- sorptive power of the soil less water is left to pass over the surface in a rainy season. 11. Improves the quantity and quality of crops. That the yield of crops is much greater on drained soils hardly needs to be substantiated. Rust, mildew, blight, etc., are much less prevalent in crops on drained soils.