40 HOFFMANN ON THE CIRCULATION 



five vascular bundles ; the salt had ascended in the prosenchy- 

 matous cellular tissue surrounding these, but not in the tracheae 

 themselves ; the latter were filled with air. The cortical layer 

 had also conducted, and indeed in the intercellular passages. 



Euphorbia terracina, L. — Treatment as in the preceding case ; 

 taken up at the end of four weeks. The solution had ascended 

 in small quantity, especially in the inner cortical layer, the liber. 

 No saline solution in the vessels of the wood. 



Hibiscus Trionum. — Watered with 1 cubic inch of the saline 

 solution during heavy rain ; taken up after three days. Only the 

 root had absorbed up to this time, and chiefly in the central 

 layer of wood, where the prosenchymatous cells in the vicinity 

 of the vessels were coloured blue in spots : the tracheae took no 

 part. 



These experiments showed that when small quantities of liquid 

 are absorbed by the root, the sap of herbaceous Dicotyledons 

 ascends, just as in the Monocotyledons above described, in the 

 cellular tissue, and with especial ease in the delicate prosen- 

 chyma surrounding the vessels; w^hile when the absorption is 

 hastened and superabundance of fluid present, the vessels also 

 take part in the conduction of the sap, at the same time propor- 

 tionately parting with the air they contain. 



2. Behaviour of the Ascending Sap in abnormal absorption. 



Salix alba. — Absorption through the exposed wood. — A young 

 leafy shoot 10 inches long was stripped of its bark for 2 inches 

 at the bottom, and dipped 1 inch in the solution ; 2 inches of 

 bark were also removed at the upper end, and this part rolled 

 up in blotting paper. Then, to prevent drying, a glass tube 

 closed at the upper end was passed over the upper half of the 

 shoot. After one day the paper was already moist and reacted 

 strongly blue ; after six days the shoot was analysed ; it was 

 filled in all parts wdth the saline solution, especially, however, 

 in the wood-vessels which were gorged with sap up to the very 

 top; much salt had crystaUized out on both surfaces of the 

 leaves, especially at the bases. Here, with the mouths of the 

 vessels of the wood standing open, a rapid ascent was observed 

 not only in the longitudinal direction, but also horizontally, into 

 the blotting paper in contact only with the alburnum. 



