. Animal and vegetable physiology considered with reference to natural theology. Natural theology; Physiology; Plant physiology; Biology. 15 16 1/. quently contains fibres, or other internal coatings, corresponding to those met with in the more compound cells. The vessels in which the internal fibres run in a spiral direction (Fig. 14), are deno- minated trachece or spiral vessels; or, from their being found very generally to contain air, they are often called air tubes* Their diameter is in general between the 1000th and the 300th part of an inch. These spiral, or air vessels, pervade extensi
. Animal and vegetable physiology considered with reference to natural theology. Natural theology; Physiology; Plant physiology; Biology. 15 16 1/. quently contains fibres, or other internal coatings, corresponding to those met with in the more compound cells. The vessels in which the internal fibres run in a spiral direction (Fig. 14), are deno- minated trachece or spiral vessels; or, from their being found very generally to contain air, they are often called air tubes* Their diameter is in general between the 1000th and the 300th part of an inch. These spiral, or air vessels, pervade extensively the vegetable system. The threads they contain are fre- quently double, treble, quadruple, or even still more numerous: they are of great length, and when the external membrane of the vessel is divided, they may easily be drawn out and uncoiled, their elas- ticity enabling them to retain their spiral shape. The object of this structure appears to be that of keeping the cavity of the tube always pervious, by * Schleiden observes, however, that spiral vessels and spiral cells occur in the living plant quite as frequently filled with sap, in the young vegetating portions, as with air in the older organs which have attained their full 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 Roget, Peter Mark, 1779-1869. London : W. Pickering
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