OF SAP IN PLANTS. 2? 



trunk a hole B was bored at 1 foot above the ground, and a 

 glass attached to catch the exuding fluid. On the following 

 day (March the 5th) the vessel at A was almost empty and was 

 refilled. In the glass at B there was no fluid ; but on March 

 the 6th ^th of a cubic inch, which reacted deep blue with sulphate 

 of iron. On the 6th the glass A was only half empty, but was 

 refilled. On March the 7th, at 2 o'clock p.m. (as usual), A was 

 half empty; nothing had flowed from B, but the orifice reacted 

 deep blue with salt of iron. A new hole C was bored ^rd of a 

 foot above the ground, on the east side, but no fluid exuded. 

 On the 8th of March A was half empty ; nothing had flowed 

 from C. On March 9th A was quite empty ; C had given off 

 nothing. 



The tree w^as cut down on the 9th of March in order to trace 

 the course by which the fluid had descended from the absorbing 

 branch to the orifice. The liber and albumen reacted blue, but 

 not the bark, heart-wood or pith. In the albumen the colouring 

 w^as streaky, and the microscope showed that it was in the 

 tracheae : these contained blue fluid with a few air-bubbles. 

 The liber was not coloured nearly so far as the woody portion ; 

 at 3 feet down the stem from the absorbing branch (on the same 

 side), the wood reacted very distinctly, but not the liber. From 

 this it follows that capacity of conducting is much inferior in the 

 liber-layer, to what it is in the tracheae of the wood. Distinct 

 reaction in blue streaks could also be observed in the trunk 

 more than 2^ feet above the branch, on the same side (but not 

 on the other) ; here the liber w^as affected, although not so 

 strongly. A transverse section showed that about |^rd of the 

 circumference of the trunk below the branch, |th above it, had 

 taken part in the diffusion of the sap : the base of the branch 

 occupied about J-th of the circumference. Dissection of the point 

 of insertion of the branch on the stem gave exactly the same 

 results as in No. 5. Examination of the wood in the vicinity of 

 the orifice, and 2 inches lower down by radial longitudinal sec- 

 tions, show'cd that the trachece had conveyed down the solution : 

 the cellular tissue and medullary rays did not react. 



It is evident, therefore, that both in normal absorption by 

 uninjured roots, and in abnormal by wounds, the conduction of 

 the spring sap occurs chiefly through the trachea and liber ; a 



