THE FUNCTIONS OF THE WOOD 195 



They are shown in Table LI. and in Fig. 23. The sub- 

 evergreen Cotoneaster behaved much in the same way 

 as did Ilex. 



CONCENTRATION OF TOTAL SAP SOLUTES. 



The general form of the curves for the concentration of 

 the wood sap in the stem of the deciduous trees examined 

 is similar viz.: There is a cusp in the early spring, fol- 

 lowed by a rapid fall.* Then a period of low concen- 

 tration in the summer and early autumn, f followed by a 

 rise, which is gradual at first, and then becomes steeper 

 as it approaches the spring maximum. So far as the 

 investigation goes, it shows that the concentration of the 

 wood sap in the root follows that of the stem, and is 

 generally lower than it; but there does not appear to be 

 such a pronounced rise in the spring, and the succeeding 

 fall is not so rapid. Accordingly, during the vernal decline 

 in concentration it is often found that the solutes of the 

 wood sap of the root exceed those of the stem. Sometimes 

 this difference persists until the concentration of the latter 

 begins to rise again e.g., Acer, Populus, and possibly 

 Fagus. 



The few observations made upon Salix indicate that 

 the concentrations in the root and the stem are closely 

 similar. 



As before mentioned, Ilex aquifolium behaves quite 

 differently from the deciduous trees with regard to the 

 seasonal variations in its wood sap. 



* This sudden rise and fall during the spring in the concentration of 

 the carbohydrates of the sap was detected by Schroder (1869) in his 

 investigation of the bleeding of trees. 



f A. Fischer (1888) also found that there was less glucose in the vessels 

 of several trees in the summer and autumn than in the spring. 



