1896.] Water Current in Cucumber Plants. 375 



them or out, as the ease may be. Such, roughly sketched, is 

 the nature of the bundle, the xylem part of which contains 5 

 or 6 spirals and from 12 to 15, or more pitted vessels. The 

 cucumber stem, exclusive of the hypocotyle, usually con- 

 tains 9 such bundles, the 5 larger ones forming an inter- 

 rupted ring or cylinder in the central part of the stem, 

 and the four smaller ones alternating with the larger ones 

 nearer the surface of the stem, the fifth bundle of the outer 

 series being usually wanting in this species. These bun- 

 dles are separated from each other by thin- walled, living 

 cells which are nearly iso-diametric. The central portion 

 of this parenchyma and that between the bundles, may be 

 designated as medullary tissue, and that farther out as cortical 

 parenchyma, although all of this fundamental tissue bears 

 chlorophyll, and is used to store starch in prior to the develop- 

 ment of the fruit. Outside of the bundles, and not far from 

 the surface of the stem, is a compact tissue formed of numer- 

 ous elongated, thick-walled, flexible, strengthening cells. 

 These are the bast fibres, forming collectively, the stereomatic 

 sheath. This sheath is several rows of cells thick and forms an 

 broken or nearly unbroken cylinder in the young stem, but 

 is afterwards ruptured longitudinally into a dozen or more 

 strands by the growth of the stem in thickness. Between these 

 strands of stereome, the cortical parenchyma finds its way to 

 the epidermis, except where the latter is specially strengthened 

 by sub-epidermal strands of collenchyma. The stem appears 

 to have so developed as to secure every advantage to be de- 

 rived from a combination of lightness with flexibility and 

 strength. 



To indicate the movement of the water in the stems and 

 leaves, various aniline stains were tried, e. g., eosine, soluble 

 nigrosene, methyl green, methyl orange, acid fuehsin, etc. 

 Eosine proved by far the most satisfactory, none of the other 

 stains moving with anything like the same rapidity, and some 

 of them causing copious precipitates in the vessels. None of 

 the substances in the sap of the cucumber vessels cause any 

 precipitate with eosine, and it is probable that dilute solutions 

 of this substance, while clearly poisonous to the plant, move 

 with the same rapidity as pure water, at least at first. 



