4 Prof. Marshall Ward, On a Problem 



Dr Russell also shows that oak a century old, and oak from 

 a bog, and even decayed wood are still active. 



Among his most interesting discoveries are, that light of 

 various kinds stimulates the activity of a piece of wood exposed 

 to it ; that the same is true of leather, cork, resin, paper, &c. ; and 

 that certain bodies — e.g. glass — are opaque to the action, whereas 

 others — e.g. porous bodies, gelatine, &c, transmit it. Moreover 

 the block of wood need not be in actual contact with the plate ; it 

 will act if an appreciable layer of air intervenes. 



For the further understanding of these and numerous other 

 interesting facts concerning the physical and chemical points con- 

 cerned, I refer the reader to Dr Russell's fascinating and im- 

 portant papers. 



My position in what follows is this. About a year ago 

 Dr Russell was so kind as to show me some of his experimental 

 results, and I was naturally much interested in his work, because, 

 apart from the more purely physical and chemical aspects of the 

 phenomena, they would appear at once to have a direct bearing on 

 the problem of the constitution of wood cell-walls. 



Beyond proposing to apply Dr Russell's results in particular 

 ways to this botanical question, and perhaps having obtained 

 certain modifications of his process and a few results of additional 

 value, I have no claims to originality in the matter, and certainly 

 no credit is due to' me as anything but a humble follower of his 

 discoveries. With these disclaimers, then, I pass to a summary of 

 my own experiments. 



I was struck at the outset with the difficulty of referring 

 Dr Russell's results to the resins, because, in the first place the 

 Larch and the Scots Pine behave so differently. 



In the Larch the resin-canals and, presumably, the bulk of the 

 resin, are in the Autumn wood zones, and it is these zones which 

 induce the strongest image ; but in the Pine, although the resin is 

 distributed in the Autumn zones as in the Larch, the most marked 

 effect is in the Spring wood. Russell finds the Larch less active 

 on the whole than the Pine, but from nay knowledge of the two 

 I should have thought them equally resinous, and their contrary 

 behaviour seems anomalous. 



But the second point strikes one as even more extraordinary if 

 resin is the active body. The Oak gives very good figures, Russell 

 placing it in the same group with the Pine as " very active." 

 Now, without saying that there is no resin in Oak, it is well 

 known that tannin and tannin-like bodies are the characteristic 

 substances in Oak, and it at once occurred to me that this series 

 of constituents ought to be tried. 



Nevertheless if we examine Russell's lists of " very active," 

 "active," and "slightly active" woods, it cannot be said off-hand 



