OF SAP IX PLANTS. 19 



elongated cells, even close in the vicinity of the former, had ab- 

 sorbed a considerable quantity of the salt, and exhibited innu- 

 merable blue dots and streaks in the longitudinal section. 



Caladium viviparum, Roxb. (Aroideae). The fluid could be 

 detected in all parts of the tuber and petiole twelve days after 

 the watering. Minute examination showed the root to be a true 

 tuber, which in three weeks after the watering was found soft- 

 ened, collapsed, and, in short, dead (probably in consequence of 

 the watering) ; on reaction it turned uniformly blue all through, 

 just as a sponge would do under similar circumstances. On 

 this tuber is seated the bulb-like base of the stem, which en- 

 closes within it the true terminal bud of the axis. Both the 

 base of the stem and the central bud exhibited distinct reaction 

 in the same way ; in longitudinal and cross sections they became 

 covered with countless blue points, which were recognized under 

 the microscope as elongated cells. A leaf-bud which had just 

 been developed from the tuber had likewise absorbed the salt, 

 especially in its central region. The investigation is difficult in 

 the fully developed leaf-stalk, since this so abounds in sap, that 

 the fluid exuding when it is cut across readily spoils the expe- 

 riment with the reagent. The blue sap is found in the elon- 

 gated cells which surround the numerous round liber-bundles of 

 the thin peripherical or cortical layer, the latter enclose isolated 

 delicate unreliable spiral vessels*. The whole of the interior of 

 the leaf-stalk is composed of parenchymatous cells, inside which 

 run not only ordinary liber-like cells with vessels, but also 

 several canals, so large that a hair may be readily introduced 

 into them. These canals, still filled with fluid in the bud above 

 mentioned, contain air in the fully developed petiole ; when the 

 latter is squeezed even six inches from a cross-cut surface, air- 

 bubbles are forced out of them ; just as was described above of 

 the Dioscorea. The walls of these air-cavities are composed of 

 large cells; these tubes therefore form a transition to those of 

 Dioscorea, which exhibit a great affinity to the ordinary pitted 



* The numerous thick- walled raphides-cells occurring here slowly expelled 

 their contents when accidentally injured, and these spread out like a tuft of 

 feathers, displaying a peculiar backward movement not unlike that of the 

 Oscillatoriese. 



2* 



