4 o TRANSPIRATION AND ASCENT OF SAP ch, 



Thawing occurred at a higher temperature than freezing, 

 no signs of melting being exhibited till 4 or 5 was 

 reached. This specimen of wood was removed from a 

 branch which had been standing some days in water. A 

 freshly cut branch of Taxus afforded - 14'5 as the freezing- 

 point. 



Owing to the pressure-effect of the ice upon the wall, 

 visibly shown by the forcible expression of drops, there 

 appeared some doubt whether this method would afford 

 any result of value. However, the experiments were per- 

 sisted in, and a length of 22 cm. by 6 mm. in diameter of 

 a yew-twig, carefully washed, was attached to the appa- 

 ratus shown in Fig. 9, in which the passage of liquid 



Fig. 9. 



through the vertically placed stick (due to a diminished 

 air-pressure in the vessel above) is shown by the move- 

 ment of mercury in the horizontal capillary tube. The 

 rate of transmission of water was observed while the tem- 

 perature of the jacket was varied. The general results 

 were as follows : 



In cooling, the current had almost ceased at 7 and, 

 completely at 11; in ivarming, it recommences feebly 

 at 5. It was impossible to fix upon any temperature 

 as the actual freezing temperature in the lumina from the 

 observations, but as all current had ceased at 11, at 

 which temperature the water in the walls was almost 

 certainly not frozen, we must conclude that these observa- 

 tions reveal no current in the walls, even of the feeblest 



