Dixon and Atkins — Variations in Osmotic Pressure, 6fc. 231 



it is only recorded in order to give some idea of the relative amounts of 

 disaccharides present. 



Not only is there a difference observable between mature and immature 

 leaves, as appears from the table above, but also between mature leaves of 

 various ages considerable differences are found, as shown in Table II. The 

 branches of Ilex seem normally to make two growths in the year. The 

 limits of these growths are defined by a crowd of small sears. Leaves may 

 be found on the last four or, in small numbers, on even the last five growths. 



Table II. 

 Ilex Aqtiifolium. 



This rise of the cryoscopic value of the sap will further very clearly be 

 seen from the averages given on page 233, for the saps of the leaves from 

 successive growths. 



This variation of the osmotic pressure with the age renders the comparison 

 of the pressures at different seasons more difficult, and makes it necessary 

 to compare the pressures of the sap of leaves of the same age. In 

 order to make this possible on each date separate determinations were 

 made on the saps derived from the leaves of the last three growtlis. The 

 leaves of the last growths were further subdivided, and separate determina- 

 tions were made on the sap from the ultimate three and from the penultimate 

 three of these latest growths. In the following Table (No. Ill) the depression 

 of the freezing-point (A) and the osmotic pressure (P) is given for each 

 sample dealt with ; and in the last pair of columns the depression and the 

 pressure of the sap pressed from the roots is added. In order to eliminate 

 as far as possible errors arising from water adhering to the surface of the 

 roots, on each occasion, before pressing the sap, the roots were dried by 

 drawing them repeatedly through air-dried soil. 



2n2 



