OF SAP IN PLANTS. 31 



appear to pour out more sap than the south. The checking 

 influence of nocturnal cold was again distinctly visible here. 



10. On the 10th of March a young sycamore stem (Acer 

 platanoides), 3 feet high and \ an inch in diameter, was plenti- 

 fully watered with solution of ferrocyanide of potassium. On 

 the 15th it was taken up, root and all. When dissected, the 

 reagents showed that absorption had not commenced in the 

 stem. At the base alone, weak, bleared blue spots were pro- 

 duced on a cross section. In one place the colour was deep and 

 sharply-defined enough to admit of microscopic examination : 

 this proved that the walls of a few streaked and spotted tracheae 

 were coloured blue. 



11. A white birch, with a trunk 1 foot in diameter, was 

 tapped 1 foot above the ground, on the west side, on the 4th of 

 March ; up to the llth nothing flowed out. On this day a new 

 orifice was made in the west side of the stem, at a height of 

 7 feet. Up to the 14th neither gave off any liquid. Only a few 

 sucking flies appeared to indicate that the sap was beginning to 

 rise. 



It is worthy of notice, how much later the bleeding occurs in 

 the birch than in the sycamore. 



12. On the 7th of March, at three o'clock, a sugar maple 

 (Acer saccharinum), with a trunk 1^ foot in diameter, was 

 tapped : 



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



B, orifice 5 feet from the ground, south side, but 1 inch 

 further to the east. 



About eight days previously several small branches had been 

 cut off further up the stem; some sap ran down from the 

 wounds. The fluid exuding from the borings was collected, 

 and gave the following results : 



March 7. 3 o'clock, at A, 3 cub. in. ; at B, 1 cub* in. 



- .- 5J .... 3* 7i .... 



8. 8 



. . 2 



.. 5 ... 



9. 7 



.. 2| ... 



- .. 5* 



