. A practical course in botany, with especial reference to its bearings on agriculture, economics, and sanitation. Botany. THE STEM 115 127. Ringing fruit trees. — The course of the sap explains why farmers sometimes hasten the ripening of fruit by the practice of ringing. As the food material cannot pass below the denuded ring, the parts above become gorged, and a pro- cess of forcing takes place. The practice, however, is not to be commended, except in rare cases, as it generally leads to the death of the ringed stem. The portion below the ring can receive no nourishment from above, and will
. A practical course in botany, with especial reference to its bearings on agriculture, economics, and sanitation. Botany. THE STEM 115 127. Ringing fruit trees. — The course of the sap explains why farmers sometimes hasten the ripening of fruit by the practice of ringing. As the food material cannot pass below the denuded ring, the parts above become gorged, and a pro- cess of forcing takes place. The practice, however, is not to be commended, except in rare cases, as it generally leads to the death of the ringed stem. The portion below the ring can receive no nourishment from above, and will gradually be so starved that it cannot even act as a carrier of crude sap to the leaves, and so the whole bough will perish. 128. Sap movement not circulation. — It must not be supposed that this flow of sap in plants is analogous to the circulation of the blood in animals, ? £„ £ though frequently spoken of in pop- ular language as the " circulation of the ; There is no central organ like the heart to regulate its flow, and the water taken up by the roots does not make a continual circuit of the plant body as the blood does of ours, but is dispersed by a process of general diffusion, partly into the air through the leaves and partly through the plant body as food, wherever it is needed. Figure 131 gives a good general idea of the movement of sap in trees, the arrows indicating the direction of the movement of the different substances. 129. Unexplained phenomena. — Though the forces named above undoubtedly exert a powerful influence over sap movement, their combined action has not been proved capable of lifting the current to a height of more than 200 feet, while in the giant redwoods of California and the tower- ing blue gums of Australia, it is known to reach a height of more than 400 feet. The active force exerted by the cell protoplasm has been suggested as an efficient cause, but as. Fio. 131.— Diagram show- ing general movement of Please n
Size: 1132px × 2206px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorand, bookcentury1900, bookdecade1910, booksubjectbotany
