Page:Mongolia, the Tangut country, and the solitudes of northern Tibet vol 2 (1876).djvu/324

296, for it supplies the plant with the lime requisite for the formation of crystals. Perhaps, it was entirely owing to the absence of these requisite conditions, that the root of the R. palmatum, as formerly cultivated in Europe, did not grate between the teeth, and was less powerful in operation than the Chinese Rhubarb of commerce, which it resembled in every other respect.

Another important circumstance is, that the principal root becomes so rotten under cultivation, that the less valuable lateral branches are alone retained for use; whereas, the pieces cut from the main root are by far the most prized. Rain-water accumulates in the cavities formed by the breaking off and decaying of the flower stalks, from which it is prevented from running off by the numerous old leaf sheaths which remain round the hilum, or eye, and in this way causes an ever-deepening and spreading decay. How this can best be prevented must be left to further experiments to determine; the remedies which appear to be most practical are: cutting away the old leaf sheaths and withered stalks before they have had time to decay at the root, and covering or stopping the eye of the stalk. Perhaps, it would be best not to allow the plants, in general, to bloom. Nearly all our larger kinds of Rhubarb, not excepting the R. palmatum, show in almost every joint of their root-leaves and of the old stipules numerous embryo buds, of which only the smallest come to maturity, because the plants must develop their flower-stalks. But, whilst old plants hardly ever throw out more than three flower-stalks, and their principal roots have seldom more than four or five root-heads, each of which has a corresponding stalk, or would have, were it not for the obstructing formation of the stem, which causes them to throw out numerous buds, these not only add more quickly to the size of the root but also form a number of shoots. Now it is just this which causes the marbled appearance with the irregular stellated spots in the parenchyma, and the more this is encouraged, so much the more will that valued structure thrive, which, as is well known, quite does away with the side branches of