OF SAP IN PLANTS. 29 



a distance of about 10 inches from the immersed lower end (the 

 root dipped in about 3 inches), the longitudinal section gave a 

 blue reaction throughout the woody substance ; the microscope 

 showed liber, tracheae and wood-cells stained ; the tracheae most 

 strongly, both in the inner and outer parts of the wood. The 

 solution had not only ascended, but also passed down as much 

 as 2 inches in small lateral branches of this root. At these points 

 the liber no longer took part in the conveyance of the fluid, 

 while many (especially the central) tracheae reacted deep blue. 



It is worth notice that the (ferruginous) soil in the vicinity of 

 the entire root acquired a blue colour from the 6th of March 

 onward ; perhaps by secretion through the peripherical parts of 

 the root, perhaps through the injured points of the little radical 

 fibres. 



8. A sycamore trunk of f of a foot diameter was bored with 

 similar holes, 1 inch deep, in two places, and all the exuding 

 fluid was caught. 



A, orifice 1 foot from the ground, south side. 



B, orifice 3 feet from the ground, south side, 1 inch further 

 westward. 



Experiment commenced at 3 o'clock on the 5th of March. 



Five o'clock : A had emitted 1 Paris cubic inch of clear watery 

 fluid; B i a cubic inch. 



March 6th, 8 A.M.: A and B had secreted nothing (cold night, 

 below freezing point). 



2 30 P.M. : A 9 cubic inches; B 12 cubic inches. 



5 30 P.M. : A and B had each given off^th of a cubic inch. 



March 7th, 8 A.M. : the flask at A and B empty. 



2 P.M. : A f ths of a cubic inch ; B J-th of a cubic inch. 



5 30 P.M. : the flasks at A and B empty. 



March 8th, the same. 



According to the foregoing, night limits the force of the cur- 

 rent (by a lower temperature). When we reflect on the unequal 

 duration of the bleeding in the trees 2 8, which all stood near 

 together, it becomes a question what was the cause of this 

 phaenomenon ? 



The varying thickness of the trunk does not seem to explain 

 the matter. No. 4 was 4 inches in diameter and bled ten days ; 

 No. 2 was 3 inches in diameter and bled five days ; No. 8 was 



