148 



above-mentioned conjecture of the retrograde motion of the sap be 

 founded, it would follow that in the subsequent vegetation the in- 

 verted would display a more vigorous growth than the proper end ; 

 and this accordingly was soon found to -be the case, with this addi- 

 tional 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. 



Analytical Experiments and Observations on Lac. By Charles Hatchett, 

 Esq. F.R.S. Read April 12, 1804. [Phil. Trans. 1804, p. 191.] 



A brief historical account of the substance here treated of is pre- 

 fixed 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 pro- 

 duction, first discover)', 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, 



