Page:Proceedings of the Royal Society of London Vol 1.djvu/168

Rh above-mentioned conjecture of the retrograde motion of the sap be founded, it would follow that in the subsequent vegetation the inverted would display a more vigorous growth than the proper end; and this accordingly was soon found to 'be the case, with this additional circumstance, that the parts beyond the buds on the inverted ends were observed to increase considerably, while the same parts on the proper ends not only withered, but even gradually died away.

In another experiment a number of cuttings of gooseberry and currant trees were planted, some in their natural erect, and others in an inverted position. Many of these, especially the gooseberry cuttings, failed altogether; but in those that survived, the same ac- cumulation of wood was observed on the upper ends of the inverted cuttings as on the vine shoots: similar effects were likewise observed in inverted grafts of the apple-tree, and in some respects also in cut- tings from the sallow—tree, where, however, they being of some length, the accumulation of wood did not take place at the summit, but about the base of the cuttings.

It will be needless to dwell minutely on these results, since they may all be deduced from the author’s theory, which, in addition to what has been above stated. is, nearly in his own words,—that the vessels of plants are not equally well calculated to carry their con- tents in opposite directions; and that the vessels of the bark, like those which constitute the venous system of animals (to which they are in many respects analogous), are provided with valves, imper- ceptible indeed to our eye on account of their extreme minuteness, but whose effects in directing the course of the sap are sufﬁciently obvious.

The paper concludes with some strictures on the experiments de- scribed by Hale and Du Hamel, and the reasons why these naturalists did not arrive at the same conclusions which are here brought for- ward, and an experiment which illustrates some parts of the paper the author gave last year on the descent of sap in trees.

A brief historical account of the substance here treated of is preﬁxed to this paper. Though long in use, especially in India, yet, except what we have lately learnt from Mr. Kerr and Mr. Saunders, few inquiries have hitherto been made concerning its mode of production, ﬁrst discovery, its nature and relative properties. We now know that it is the nidus or comb of the .insect called Coccus, or Chermes Lacca, deposited on branches of certain species of Mimosa and other plants; and that the kingdom of Assam furnishes it in the greatest quantity. There are four sorts of it :—1. The stick lac, being the substance or comb in its natural state, incrusting small branches or twigs. 2. Seed lac, or the same substance granulated, but probably prepared in some manner, it being deprived of a great part of its colouring matter. 3. Lump lac, formed from seed lac,