THE MOVEMENT OF WATER IN PLANTS. 



The composition of the fluid obtained from a Birch in the spring 

 was found by Schroder to be the following : 



i litre contained 



Ash 0-52 grms. 



Sugar (Levulose) ... ... 12*00 



Proteid 0*02 



Malic acid 0*51 



Schroder confirmed Knight's observation that the proportion of sugar is 

 less the higher the part of the tree from which the fluid is taken, and he 

 found that this was generally true of the other substances also. 



But the root-pressure does not only manifest itself by 

 causing a flow of sap from the cut surfaces of plants ; it also 

 causes, in many plants, the exudation of drops of sap at the 

 free surface. Thus drops may commonly be seen on the sur- 



FIG. 19 (after Gardiner): A, section of leaf of Saxifraga crustata, shewing the 

 water-gland, e, which is continuous at its base with a fibro- vascular bundle ; 

 w, water-pore; b, hairs to which the deposit of calcium carbonate becomes 

 attached on the evaporation of the exuded drops of water. 

 B, cells of the gland more highly magnified. 



face of certain Fungi (Pilobolus crystallinus, Penicillium glau- 

 cum, Merulitis lacrimans] which have been doubtless exuded 

 as a consequence of the hydrostatic pressure existing in the 



