JN VEGETABLE BIOLOGY. 257 



and those of its cell-walls. Thus we see that the lignified walls 

 of the Rose, Aran do, and Maize, and the xylem of the Fig give 

 the three proteid reactions, and stain yellow or brown with 

 iodine, green with methyl-green, bright pink with corallin-soda, 

 and with picric-blue yellow, while they refuse to take up borax 

 carmine. These reactions are also given by a solution of catechu 

 and by the iron- greening tannin of the Ivy — some being given 

 too by the iron-blueing tannin of the Rose and the Primrose. 



Further, we can get iron-greening tannin-reactions in these 



walls, whose behaviour, moreover, to the (C) and Grnezda's tests 

 closely resembles that of the tannins, and is quite unlike that of 

 proteids. There are, however, in the walls of Jiosa canina 

 indications of the presence of two kinds of tannin, the iron- 

 blueing kind showing itself in the fundamental tissue, soft bast, 



and cambium. Now, the presence in the tissues of the Rose of 



an iron-greening as well as an iron-blueing tannin was men- 

 tioned in the memoir on tannin *, and several experiments proved 

 conclusively that many of the reactions already given as charac- 

 teristic of iron-2reenin£ and of iron-blueing tannin can be 

 obtained when the tissues of the Dog-Eose (fundamental tissue 

 of young stem, epiderm, and hairs) are examined. 



The xylem and hard bast of the Eose agree thoroughly in 

 their reactions, all of which can be explained on the supposi- 

 tion that there is an iron-greening tannin, or a derivative of 

 such, still behaving in the same way to dyes, &c, in the walls of 

 these tissues. With regard to the other tissues, especially tho 

 collenchyma, the evidence is not so plain. An iron-blueing 

 tannin is clearly present here, and by mixing solutions of tannic 

 acid and of catechu in a certain proportion, and precipitating 

 with Schulze's solution, one can closely match the colour taken 

 by the collenchyma with that reagent. This and some other 

 reactions would seem to imply the presence of two tannins, an 

 iron-greening and an iron-blueing, in these walls ; nor should this 

 excite surprise, seeing that Dufour has found both kinds ot 

 tannin in the epiderm of Sedum Telephium, while the same thing 

 occurs in the Eose, and, as will hereafter appear, in the Fig as 

 well. But it must be remembered that in these matters we 

 are working quite in the dark ; as, irrespective of other sub- 

 stances which undoubtedly are present in the cell-walls, we 



# Journ. Linn. Soc, Bot. vol. xxvii. p. 530. 



