1896.] Water Current in Cucumber Plants. 373 



stakes or over high strung wires. A sharp razor was used in 

 cutting the stems. 



Before proceeding to the experiments, it will be necessary 

 for the sake of those who are not familiar with the structure 

 of the cucumber stem, to briefly indicate its anatomy. The 

 bundles are bi-col lateral, i. e., there is a group of phloem on 

 the inner, as well as on the outer face of the bundle. The 

 outer phloem is separated from the central strand of xylem 

 by a cambium zone, which is restricted to the bundle, i. e., not 

 inter-fascicular. The inner phloem is separated from the 

 xylem, by a meristematic tissue structurally much like cam- 

 bium, but functionally different. The phloem consists of 

 numerous large sieve tubes, with the usual accompanying cells 

 and cambiform cells. The central or xylem strand of the bun- 

 dle consists principally of large pitted vessels, held together by 

 shorter tracheids and lignified parenchyma. The mode of ori- 

 gin of the pitted vessels, i. e., out of a series of large superposed 

 cells, is plainly visible, the cross septa being sometimes pres- 

 ent and perfect, but more often partially wanting or reduced 

 to mere rims on the inside of a continuous tube. The walls 

 of these tubes contain thousands of very thin places, or actual 

 perforations, (in many cases the central slit takes no stain), and 

 the tubes appear to be admirably adapted for water reservoirs, 

 any adjacent portion of the plant being clearly able to draw 

 from them without hindrance. It appears to me somewhat 

 doubtful, whether they also function as direct water carriers. 

 This business seems more suited to the spiral vessels which 

 occur in a little group on the inner face of the xylem strand, 

 embedded in a delicate, non-lignified living parenchyma, 

 which frequently contains chlorophyll. The walls of these 

 spirals are not pitted ; their bore is almost capillary, i. e., much 

 less than that of the pitted vessels ; and they are of great 

 length, probably by means of splicings extending as open 

 tubes the whole length of the vine. That they are of more 

 fundamental importance to the plant than are the pitted ves- 

 sels, appears from the fact, that they are the only tubular 

 parts of the xylem to be found in the smaller roots, and are also 

 the only xylem-vessels passing out of the stems into the peti- 



