ON SOME N.S.W. TAN-SUBSTANCES. 201 



root sold by herbalists and others in Europe, under the name of 

 Bistort and Snakeweed root. After suitable preparation the roots 

 of this and some other species are used as food in some countries, 

 on account of the starch they contain, and it is quite possible that 

 the hungry Australian aboriginal may have put the species which 

 are found in this part of the world to the same use, though I have 

 never seen it recorded. 



The leaves of P. tinctorium yield a kind of indigo in France, 

 while the Chinese produce a blue dye from several species. 



But up to the present it appears that P. amphibium is most 

 used as a tan-substance. H. R. Procter in his admirable " Text- 

 book of Tanning," and the " Year-book of facts in Science and 

 Art, 1876," both draw attention to it. It is an annual, abundant 

 in the Missouri Valley, United States, and can be mown and 

 stacked like hay. It is largely used in the Chicago tanneries, and is 

 said to give a leather which is tougher, more durable, of finer 

 texture, and capable of higher polish, than that tanned with Oak 

 bark. The process is said to be the same. 



Consideration of these facts shows us that our native species of 

 Polygonum are well worthy of examination. P. plebejum, for 

 instance, occurs plentifully along rivers, creeks, and moist localities 

 and in most places it could be mowed down. In handling the 

 plant during the operation of drying it irritates to sneezing, though 

 only slightly. The irritation was increased during the operation 

 of grinding the dried plant for the purpose of these experiments. 



Extract. — 28*11 per cent, to water at 100° C, yielding a 

 solution of a light reddish-brown, very similar to that yielded by 

 Eucalyptus corymbosa bark, though not so bright in colour. Colour 

 of moist residue dirty dark brown, interspersed with a, few light 

 particles. 



Tannic acid — 11*19 per cent. 



It will be interesting to compare with this result the following 

 analyses of two of the species of Polygonum referred to above. I 

 am unable to find the names of the chemists who made the 

 analyses, nor are the particulars as explicit in all cases as I could 

 wish, but I quote my sources of information : 



Polygonum Bistorta : 



Tannin. 





(Roots presumably) ... 



17*1 pei 



r cent 



"Spring," 



... 21*1 



55 



" From botanic garden," 



... 17*0 



JJ 



" Leaves in the fall," 



4*2 



55 



" Waste of roots," ... 



..... 16*0 



55 



Polygonun sp. 







" Fall Polygonum from the Marsh," 



... 20*0 



55 



Summer ditto ditto 



... 26*4 



55 



C. T. Davis, " The Manufacture of Leather. 1 

 N- October 5, 1887. 



