1 86 TRANSPIRATION AND ASCENT OF SAP ch. 



The result, however, was not anticipated, as from 

 Andre's work it appeared that the proportions of the 

 solutes present in the sap were not altered by their 

 passage out of the organs under pressure. Hence it was 

 to be expected that the ratio of the electrolytes to the 

 other solutes would remain sensibly the same for the sap 

 pressed from the living tissues and for that from tissues 

 rendered permeable by liquid air. 



The results for the rhizome of Iris germanica and for 

 the fruit of Citrus limonum are exceptions, for in their 

 case the sap extracted after freezing appears to contain 

 a larger proportion of electrolytes to other solutes. This 

 may very probably be assigned to actual differences in the 

 sap from two apparently similar portions of the same 

 massive organ. It is also possible that part of this effect 

 is due to the greater viscosity of the sap from the treated 

 organ. 



These two factors probably also account for the anoma- 

 lous fall in conductivity noticed in the sap of the fruit 

 Pyrus malus and of Vitis vinifera obtained by means of 

 liquid air. 



It is certain that a much less extreme cold than that of 

 liquid air would render the protoplasm permeable ; but 

 where this is available, it has the advantage of being very 

 rapid in its application, and reduces the chances of change 

 in the sap to a minimum. 



Use of heat and chloroform vapour for the 

 extraction. A few experiments were made with the 

 object of finding out if the application of heat in a 

 saturated atmosphere, or the exposure to chloroform 

 vapour, might be used as a substitute for exposure to 

 liquid air. 



First, with regard to the application of heat, a quantity 

 of leaves of Ilex aquifolium were divided down the midrib, 

 and two samples, A and B, were formed, each containing 

 half of every leaf used. A was wrapped in moist bibulous 



