OF SAP IN' 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 unroUable 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 

 Oscillatorieae. 



2* 



