. An introduction to vegetable physiology. Plant physiology. OTHEK METHODS OP OBTAINING POOD 201 root-branches and a root of a suitable host, a curious sucker- like body is developed at the point of contact (fig. 99). This is a kind of parenchymatous cushion, which partly surrounds the host, and from the inner side of its con- cavity certain absorption-cells grow out and penetrate into the former, pushing their way until they reach the centre of the invaded root (fig. 100). These absorbing organs are often erroneously spoken of as roots. They cannot properly be so called, as they are developed
. An introduction to vegetable physiology. Plant physiology. OTHEK METHODS OP OBTAINING POOD 201 root-branches and a root of a suitable host, a curious sucker- like body is developed at the point of contact (fig. 99). This is a kind of parenchymatous cushion, which partly surrounds the host, and from the inner side of its con- cavity certain absorption-cells grow out and penetrate into the former, pushing their way until they reach the centre of the invaded root (fig. 100). These absorbing organs are often erroneously spoken of as roots. They cannot properly be so called, as they are developed from the cortex of the rootlet, and not, as root- branches are, from the tissue of the peri- cycle. They are best spoken of as haus- toria, a term which is purely physiological, and carries with it no anatomical signifi- cance. "While the root is setting up this rela- tionship with a host plant, the shoot of the seedling is growing normally. Its leaves and other sub-aerial parts are well developed and discharge their appropriate functions. The plants would not be recognised at all as in any way parasitic without an examination of the subterranean parts. They absorb certain nutritive materials from the roots on wbich they fix themselves, and generally destroy them. The damage is, however, local, and does not involve the death of the host plant. Indeed, many of these root-parasites do so little, harm to the latter that an affected host is often not noticeably different in appearance from a neighbouring plant of the same species which is not Fig. 100.—Thesium aVpinum. Piece op a BOOT WITH SUCKER IN SECTION. X 35. (After Kerner.). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Green, J. Reynolds (Joseph Reynolds), 1848-1914. Philadelphia, P. Blakiston
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