concerning Wood and Lignified cell-walls. 9 



attribute the fuzzy outlines to their being moist — for the ordinary 

 drying alone afforded to the shavings, left them by no means 

 really dry. 



In these cases, then, it seemed impossible to suppose that the 

 active body could be a Resin ; and, not unnaturally with such wood 

 as Oak, one thought of Tannin or some such body as Gallic or 

 Tannic acid as a possible factor. 



In experiment No. 28, the same piece of wood was used as in 

 No. 8, but before putting it on the plate half the piece was painted 

 over with a camel-hair pencil dipped in a weak solution of pyro- 

 gallol, and a streak of the same was drawn across the middle of the 

 untreated half, and the section then dried between filter-paper. 



After incubation for 11 days at 20 — 22° C, a sharp image was 

 obtained particularly dark at the parts impregnated with the pyro- 

 gallol, rendering it more than probable that my surmise was right. 



I then instituted a set of trials with various bodies, more or 

 less directly derived from wood, with a view to seeing if they gave 

 similar results. 



Clove oil was used on Brownea grandiceps, on a section which 

 (experiment No. 3) had given no good results at 20 — 22° for 12 

 days. The treated section at 20 — 22° for six days yielded no trace 

 at all : it seemed as if the clove oil had stopped the action, but, 

 since the incubation-period was shortened, the trial was not con- 

 clusive in this respect. 



Hemitelia integrifolia, which gave similar results to the fore- 

 going when not treated (experiment No. 4), was similarly tested 

 with clove oil, and incubated for nearly the same period (11 days) 

 at 20 — 22° (experiment 26), and the effects of the clove oil in 

 deepening the action were at once apparent, the effect showing 

 even on the paper into which the oil had diffused. 



Here, then, we must conclude that clove oil is also an active 

 agent, though the experiments do not decide whether it is so 

 alone, or only in contact with some other body in the wood. 



The next substance tried was tannin. As Exp. Nos. 1 and 7 

 showed, Aristolochia Sipho was very inactive in eight days at 

 20 — 22° C, while Vitis Labrusca seemed utterly without action 

 even after 12 days' incubation. After being washed in a weak 

 tannin solution and then dried, however, the same sections gave 

 good images in 11 days and 12 days respectively, at the same 

 temperature, the Vitis being especially active. 



Tannin would therefore appear to be a markedly efficient agent, 

 and the fact suggests an explanation why Oak is such a " very 

 active " wood. 



I then tried pyro-gallol. As already shown, this was decidedly 

 successful as evinced by streaking the Oak section (Exp. No. 28) ; 

 but its activity was even more clearly evident with Ulmus cam- 



