58 TRANSPIRATION AND ASCENT OF SAP ch. 



five minutes' rotation is collected. The quantities of sap 

 obtained in this way are surprising. Whether in spring, mid- 

 summer, autumn, or winter, I have found that four such 

 pieces of the various woods used yielded about 3-5 c.c. 

 In the same way, sap was collected from pieces of steamed 

 branches. These samples of sap could now be compared 

 physically and chemically. In every case, as was antici- 

 pated, profound differences were found to exist between 

 the characters of the saps drawn from the fresh and the 

 steamed branches. Some of the results may be seen in 

 Table 4 : under A the depression of the freezing-point, under 

 C the electric conductivity is given. Also the reaction 

 of the sap to litmus and the presence of oxydase are 

 noted : 



Table 4. 

 Changes introduced into Wood-sap by Steaming. 



The change in A brought about by steaming is due to 

 the total increase of the dissolved substances, and indicates 

 that the concentration of the sap has increased four to six 

 times. The changes in conductivity (expressed as the 



