. Cyclopedia de cultures agricoles. Produits agricoles ; l'Agriculture. Fig. 26. Touchez-racine. Pissenlit. La plus grande partie de ce produit à la vitesse de mille pieds par jour. En raison du besoin d'air, la plupart des racines sont en mesure de prospérer dans des sols humides, et leur meilleur travail est fait dans le sol où l'eau est tenue dans un mince film autour le sol-particules. Chaque particule constitue une minute réservoir d'eau. Pour atteindre et appuyez sur ces réservoirs est le travail de la racine-poils, qui ap- poire juste arrière de l'apex racinaire comme des excroissances de la surface des cellules de la racine (Fig. 28 et 29). Ils se forcent énergiquement

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. Cyclopedia of farm crops. Farm produce; Agriculture. Fig. 26. Tap-root. Dandelion. the greater part of this being produced at the rate of a thousand feet per day. Because of need of air, most roots are unable to thrive in wet soil, and their best work is done in soil in which the water is held in a thin film around the soil-particles. Each particle constitutes a minute water reservoir. To reach and tap these reservoirs is the work of the root-hairs, which ap- pear just back of the root-tip as outgrowths from the surface cells of the root (Figs. 28 and 29). They force themselves energetically between the soil-particles and attach themselves so closely that they often break oif rather than loosen their hold when the root is pulled up. Thus they come into contact with the water-films that surround the particles, and by means of water-attracting sub- stances within the root-hair they pull the water away from the particles. As each tiny reservoir is emptied of its supply, water flows in from surrounding ones and these also yield up their stores. The water passes from the root-hair through the soft outer tissue (cortex) to the wood-cells, in which it passes directly to the leaves. These i;hick-walled wood- cells form groups that al- ternate with groups of thin- walled tissue or bast which conveys proteids and other food from the leaves to the root and to other parts of the plant. The wood and bast are surrounded by a row of small cells (endoder- mis), whose closely joined walls prevent the entrance of air, which would im- pede the progress of water in the wood-cells. The absorptive surface of the root may be in- creased from seven to seventy-five times by the root- hairs. The fine roots, on which the root-hairs are principally produced, are known as "feeding roots, " and all tillage should be practiced with special reference to them. Tillage aids the work of the root by increasing the air and water-supply, and by loosening the soil. Roots will penetrate hard so

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