92 PROPAGATION OF PLANTS. 



vine, has long been practised for the purpose of produc- 

 ing extra large specimens of jfrnit, it becoming gorged 

 with organizable matter, which is prevented from passing- 

 downward on account of the removal of the ring of bark. 

 The pojver ojjQejj^oapgro^riaje^^fcaiji elements and 

 not others "can scarcelylBe doubted, ami otigti we know 

 but little of the process, but it is through the individu- 

 ality of their functions that they are enabled to take from 

 the liquids passing through them those materials neces- 

 sary for their own growth, allowing others to pass unap- 

 propriated ; thus certain groups of cells assume one form, 

 size, color, as in the case of the double or quadruple 

 grafted Pear tree, each group retaining its own individu- 

 ality to the end. This preservation of individual charac- 

 teristics of cells^ may not only be seen in the multiple 

 steins of grafted trees, but frequently in various simple 

 herbaceous plants, as in the stems and leaves of the 

 Japan Zebra Grass (Eulalia), and in the Variegated Rush 

 (Scirpus), shown in figure 42. In both of these plants 

 the long, slender leaves and stems are composed of alter- 

 nate sections of white and green parts, and if we take no 

 account of any downward flow of organizable matter, and 

 presume that the crude sap is assimilated in its progress 

 upward through the leaves, we still find it difficult to 

 explain how the green colored liquids can pass through 

 the white parts and leave no stain of chlorophyll, except 

 upon the hypothesis that there is an individuality of 

 action in the various groups of cells of the leaves which 

 enables them to retain their distinct characteristics, while 

 all are drawing nutrients from the same source and 

 through the same set of vessels. We know that some 

 such action takes place in grafted trees with stems and 

 roots made up of different species. Quince roots may 

 imbibe nutrients from the soil, while Pear leaves may as- 

 similate them ; yet each remain true to its species or vari- 

 ety. Conductibility in this case is not only a function of 



