140 Report on the Caoutchouc Tree of Assam. {Feb. 



Cecropia peltata yielding the American caoutchouc, as its juice is diffi- 

 cult to inspissate*. 



The order Euphorbiacea would likewise appear to supply a large 

 quantity. Thus Dr. Lindly 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 Apocquese are also reported to produce good caoutchoucf ; thus 

 Aricola elastica produces the caoutchouc of Sumatra ; and it is from 

 this plant that caoutchouc has been produced in Penang and exported 

 to England J. Willughbeia edulis is likewise an Indian plant from 

 which caoutchouc has been produced, but Roxburgh says it is of indif- 

 ferent quality ; unless I have been misled, good caoutchouc is obtained 

 from Nerium grandifloreum of Roxburgh. 



It is probably equally abundant in Asclepiadea ; one plant of which 

 order Cynanchum albifloreum has been stated to yield it of excellent 

 quality in Penang. Mr. Royle seems inclined to attribute the great 

 tenacity of the fibres of some plants of both these orders to its presence, 

 but this supposition seems to me of very doubtful accuracy§. 



It is to these orders therefore, viz. Tritecia, Euphorbiacea, Apocquea, 

 and Asclepiadea that I would beg to direct particular attention. The 

 relative values of the various caoutchoucs is still open to investigation. 

 The relative values of the milky juice as sources of caoutchouc depend 

 on their freedom from viscidity, and this is very readily ascertained by 

 rubbing up a few drops in the palm of the hand : in freedom from this 

 material nothing can well exceed the juice of the Ficus elastica. 



Too much attention in fact can scarcely be paid to all plants afford- 

 ing milky juice ; as in the event of a diminution in quantity from the 

 present sources, chemists may possibly devise some means of extracting 

 it from those materials, which at present are disregarded. This of 

 course, only holds good provided the assumption that the juice of 

 all plants of a milky nature contains caoutchouc, proves correct. A 

 historical retrospect of caoutchouc may be found in the Mechanic's Maga- 

 zine, vol. 24, page 434. In this the opinions of Dr. Anderson, ont he 

 probable future extensive utility of this substance are given at length ; 

 the author however appears to consider these views as overdrawn, and 



* Lindly's Introduction to Natural system of Botany, p. 176. 

 f Lindly's Instructions, p. 300. 



J Royle's Illustrations, p. 329, under Euphorbiacea, and p. 270, under 

 Apocquea. 



§ Royle's Illustrations, p. 274- 



