OF SAP IN PLANTS. 21 



almost all of the plants mentioned above, so far as the researches 

 here described go to show. The transverse section showed that 

 the salt had perfectly penetrated this, with the exception of the 

 yellowish vascular bundles which run in the thick parenchy- 

 matous cylinder ; otherwise a great quantity of dark blue cells 

 were found in all parts among the uniformly light blue mass of 

 cells. In the lower parts of the stem the reaction was only 

 weak ; it was more distinct in the peripherical part (no rind ex- 

 isted here) further up ; it was strongest at the apex, where the 

 separate flowering branches go off, for here not only the periphery 

 but also the interior of the stem was closely sown with blue 

 spots (streaks in the longitudinal section), which under the mi- 

 croscope were seen to be elongated cells : the angular, dotted, 

 and small streaked vessels which were situated partly near the 

 periphery and partly deep in the parenchyma of the stem, con- 

 tained air and had no share of the colouring. 



III. Dicotyledons. 



In these plants we meet with a phagnomenon which is not 

 observed in those divisions of the vegetable kingdom above in- 

 vestigated, at all events not in Germany, namely, the ^* bleed- 

 ing,^^ or "tears,^^ which occur on wounds of many of the shrubs 

 and trees of this division in early spring. 



This phaenomenon is so peculiar that it will be advantageous 

 to examine it separately. In the following experiments I inves- 

 tigated, 1st, the course of the spring sap ; and 2ndly, that of the 

 summer sap, independently. 



1. The Spring Sap, 



1. On the 27th of February 1850, a root A, of ^ an inch dia- 

 meter, coming from the west side of a white birch 6 inches in 

 diameter, was laid bare, cut across, and the upper cut end placed 

 in a cylindrical glass, of about 1 cubic inch capacity, filled with 

 a solution of ferrocyanide of potassium. This was done at four 

 o'clock in the afternoon. By the next morning the fluid was 

 absorbed as far as the root reached. 



On the 27th also, several holes of 1| line diameter were bored 

 i an inch deep, and into these introduced and cemented quills 



