198 SOME RECENT RESEARCHES IN PLANT PHYSIOLOGY 



level in the tree is associated with a change in concen- 

 tration.* 



The subject for the investigation was an old tree which 

 had been cut across near the ground many years previously. 

 From the level of the soil three similar branches about 

 30 centimetres in diameter took their origin, and rose to 

 a height of about 10 metres. One of these was cut down 

 in the middle of October, and samples of the wood excised 

 at various levels viz.: (1) ground-level, at (2) 2 metres, 

 (3) 4 metres, (4) 6 metres, and at (5) 8 metres above 

 ground-level, and finally (6) from the small branches 

 about 10 metres above the ground. The following table 

 gives the results of determinations made on the sap cen- 

 trifuged from the wood, and shows how the concentration 

 varies from below upwards at that time of year : 



TABLE LII. 



Acer macrophyllum : WOOD SAP, OCTOBER. 



* Schroder (1869) found this to be the case in bleeding sap of Acer 

 platanoides and Betula. The sugar concentration in Acer was found 

 to be greater in the root and in the upper parts of the stem than in the 

 lower parts of the stem. In Betula, on the contrary, the concentration 

 of the bleeding sap is less in the top of the stem and in the root than 

 it is in the base of the stem. 



