Page:An introduction to physiological and systematical botany (1st edition).djvu/89

 Rh just described, when cut across shows something of a circular arrangement of fibres, arising from the original disposition of the leaves. The common orange lily, Lilium bulbiferum, Curt. Mag. t. 36, and white lily, L. candidum, t. 278, which belong to the same natural family of monocotyledones, serve to elucidate this subject. Their stems, though of only annual duration, are formed nearly on the same principle as that of a Palm, and are really congeries of leaves rising one above another, and united by their bases into an apparent stem. In these the spiral coats of the sap-vessels are very easily discernible.

To conclude this subject of the propulsion of the sap, it is necessary to say a few words on the power which the vessels of plants are reported to possess of conveying their appropriate fluids equally well in either direction; or, in other words, that it is indifferent whether a cutting of any kind be planted with its upper or lower end in the ground. On this subject also Mr. Knight has afforded us new information, by observing that, in cuttings so treated, the returning vessels retain so much of their original nature as to deposit new wood