34 TRANSPIRATION AND ASCENT OF SAP ch. 



razor was to compress it from the cell-wall upon the one 

 side over the section. 



Similar experiments were made on elm and lime, with 

 the added precaution of removing the paraffin or gelatine 

 at the ends without cutting or removing any of the wood. 

 This was effected by careful use of the razor, the object 

 being to avoid as far as possible laying open the lumina 

 of conduits the terminal walls of which might lie upon the 

 surface of the section. In the case of elm and lime again, 

 sections taken about half a millimetre from the end showed 

 areas over which the filling with paraffin was complete, and 

 yet deep staining of the intervening walls. Longitudinal 

 sections near the end confirmed this appearance ; the 

 lumina seemed quite filled. In these cases the removal 

 of the branches from the hot paraffin was effected gradually, 

 to secure, so far as possible, that solidification and shrink- 

 age should proceed slowly from above downwards, and 

 thus guard against shrinkage leading to the withdrawal 

 of the paraffin out of contact with the wall. Again, the 

 branches of lime treated for comparison with gelatine 

 revealed areas in the cross-sections completely injected 

 with gelatine and having the walls deeply stained. Thus 

 we see that both in those experiments in which the lumina 

 were choked with paraffin and in those in which the 

 lumina were choked with gelatine there was at least 

 a feeble upward motion of the solution of saffranine 

 in the walls. Lime branches treated with paraffin, in 

 some places close to the cut surface, showed the pene- 

 tration of this into the protoplasm-filled cells, permeating 

 their contents. High up, only the larger vessels were 

 filled with paraffin. 



The result of these experiments may be summed up as 

 follows : 



The stoppage of the lumina and the freedom of the cell- 

 wall is preserved by the use of paraffin, and, possibly, by 

 th at of gelatine. 



