304 Mr D. Don an the Rhubarb of Commerce* 



that, consequently, 2d, It is not by an effect of the will of the 

 animal or by that of certain passions, that this light emanates 

 fromgts eyes ; 6d, That this shining does not manifest itself in 

 absolute or too profound darkness ; 4th, That it cannot enable 

 the animal to move with security in the dark. — Biblioth. Britan- 

 nique, T. 45. 



Remarks on the Rhubarb of Commerce, the Purple-coned Fir of 

 Nepal, and the Mustard Tree. By Mr David Don, Libra- 

 rian of the Linnean Society, Member of the Imperial Aca- 

 demy Naturae Curiosorum, of the Wernerian Society, &c. 

 Communicated by the Author. 



I 



1. On the Rhubarb of Commerce, 



.T is well known that the plant which yields the rhubarb 

 of commerce has been hitherto involved in much obscurity, 

 and hence there have arisen many discordant opinions, both 

 among botanists and pharmacologists, respecting the species 

 of Rheum which affords this valuable medicinal root. They 

 judged it rightly to be the produce of a species of Rheum, 

 but of what particular species, without authentic materials it 

 was impossible for them to decide. Linnaeus considered it at 

 first as the produce of his Rheum rhabarbarum or undulatum, 

 but he afterwards appears to have altered his opinion in fa- 

 vour of Rheum palmatum ; " while Pallas, who certainly had 

 better opportunities of gaining correct information on the sub- 

 ject, regarded it as composed chiefly of the roots of Rheum un- 

 dulatum and compactum. Mr Sievers, an enterprising assistant 

 of Professor Pallas, and well known by his interesting Letters 

 on Siberia, published in the Nordische Beytrdge, was sent by 

 the Empress Catharine II. purposely to try to obtain the true 

 rhubarb plant from its native country ; and although, after tra- 

 velling for seven years in the countries adjacent to that in which 

 it is found, he was unable to effect the object of his mission, 

 yet he obtained sufficient information to convince him that the 

 plant was then unknown to botanists. But it was reserved for 

 Dr Wallich, the zealous superintendent of the Calcutta Botanic 

 Garden, to set this long agitated question at rest, by the trans- 

 mission of seeds and dried specimens of the true rhubarb plant 



