478 hitelligence and Miscellaneous Articles. 



It is impossible not to be struck with the analogy of the soluble 

 compound with orcin, and that of purpurate of ammonia with orcein. 

 By heating orcin with dilute nitric acid, and adding ammonia, the 

 solution assumes a very deep red colour, which, however, is never 

 so fine as that of the orcein of M. Robiquet. — L'Institut, March 1838. 



LACTATE OF UREA. 

 MM. Cap and Henri by treating lactate of lime with oxalate of 

 urea obtained lactate of urea, which crystallizes in very white pris- 

 matic needles, and possesses very distinct chemical characters. This 

 lactate has also been found by them in a natural state ; after having 

 separated the free lactic acid from urine by an excess of hydrate 

 of zinc, they obtained this salt in crystals, and perfectly identical 

 with that prepared by direct combination. — L'Institut, March 1838. 



CAOUTCHOUC IN PLANTS.* 



The substance caoutchouc is a widely disseminated constituent of 

 vegetable fluids. It has hitherto, I believe, been found only in plants 

 with milky juice, although its presence in all plants yielding such 

 fluid remains to be proved. The presence of caoutchouc in silk has 

 been, I believe, attributed to the nature of the fluids of the plants 

 on which the caterpillars feed ; but this, although applicable to the 

 mulberry plants, can scarcely hold good with the various species of 

 Tetranthera on which the Moonga feeds, or with the castor-oil plant, 

 the chief food of the Eria, which in Assam does not appear to yield 

 milk. Milky juice is often characteristic of certain families, but 

 often not ; its presence is frequently of importance, as it often af- 

 fords valuable indications of aflinity. It is remarkable that it is al- 

 most unknown in the grand division of Monocotyledonous plants. 

 The families in which its presence may be said to be universal are 

 Apocquea, Asclepiadea, Campanulacea, Sobeliacea and the great divi- 

 sion of Compositce, Ckicoracea, of which the lettuce is a familiar ex- 

 ample. It is of common occurrence in EupJiorhiacea and Tulicea, 

 which orders may be looked on as the grand sources of caoutchouc. 

 Thus, in addition to our Indian plants, the American caoutchouc is 

 supposed to be produced by Cecropia peltata, which belongs to Ur- 

 ticea, and the ule tree of Papantla, from which the caoutchouc of that 

 country is obtained, is supposed to belong to the same orders, I 

 must, however, observe that Baron Humboldt objects to the suppo- 

 sition of Cecropia peltata yielding the American caoutchouc, as its 

 juice is difiicult to inspissatef. 



The order Enphorbiacea would likewise appear to supply a large 

 quantity. Thus Dr. Lindley informs us that the true caoutchouc is 

 furnished by Siphonia elastica, Hevia quiancusis of Aublet, a Surinam 

 and Brazilian tree ; and it is from a tree of this order that a substance 

 resembling caoutchouc is procured in Sierra Leone. 



Some ApocquecE are also reported to produce good caoutchouc J ; 

 thus Aricola elastica produces the caoutchouc of Sumatra, and it is 



• From Mr. Wm. Griffith's Report. Journ. of the Asiatic Soc. of Bengal, 

 t Lindley 's Introduction to Natural System of Botany, p. 17G. 

 j Lindley's Instructions, p. 300. 



