OF SAP IN PLANTS. 17 



(vide Rhapis flabelliformis above), except that the vascular 

 bundles of the true axis are very irregularly scattered in the 

 interior, while they are arranged in a tolerably even radial order 

 towards the circumference. In the main axis itself the salt 

 could not be demonstrated with sufficient certainty at this time, 

 but with the greatest ease in the sheath (the base of a leaf) which 

 tirmly enveloped the whole main axis. Here the blue points 

 were found in greatest abundance close beneath the outer epi- 

 dermis, but also in large numbers immediately surrounding the 

 liber bundles (enclosing unreliable spiral vessels). The micro- 

 scope proved that the blue colour existed exclusively in uncom- 

 monly continuously stained cellules (containing large nuclei) 

 arranged in very straight longitudinal rows close beside the vas- 

 cular bundles. The arrangement of the spiral vessels, liber- 

 bundles and sap-conduits in the leaves was similar to that in 

 the stem. 



Panicum plicatum, Lam. (Graminaceae). Had not absorbed 

 the least in four weeks ; the same happened in Ruscus aculeatus 

 and Ananassa sativa. 



Arum divaricatum, L. (Aroideae). These plants had, for the 

 most part, absorbed nothing at all even after four months ; in 

 the few cases in which a weak reaction could be detected in the 

 tuber, the blue colour was found in the large parenchymatous 

 cells of the general substance, which contained the unusually 

 thick starch-granules, of beautiful pyramidal and polyhedral 

 forms with rounded faces ; while the scattered yellowish bundles 

 of partly round, partly angular annular vessels were never dis- 

 coloured. 



Tradescantia discolor, L'Herit. (Commelinaceae). The reac- 

 tion was visible in the stem in four days after the watering. The 

 investigation is most difficult in the upper leafy parts, although 

 they are coloured deepest, because immediately the cortical 

 layer is cut across a great quantity of thick gummy liquid 

 exudes, which covers the whole surface of the section and con- 

 founds all the previously distinct fluids together. But when the 

 stem is cut lower down, a few inches from the ground, the in- 

 terior is found far less rich in sap, only a little mucilage exudes, 

 and it is more clearly seen when the absorption of the salt has 



SCIEN. MEM. Nat. Hist. VOL. I. PART I. 2 



