2'20 FALSE GRAFTS. GENERAL COURSE OF THE SAP. 



352. Errors in regard to the success of the process have 

 arisen from an occurrence that sometimes takes place, the 

 formation, by the graft, of independent roots, which supply it 

 partly or wholly with nourishment, with little or no assistance 

 from the stock. In this way has been explained the fact, that 

 the Olive has been made to grow upon the Fig tree (as recorded 

 by Columella, one of the earliest writers upon Agriculture) ; for 

 no proper union can take place between them, on account of 

 the wide difference in their character. Mention is made by 

 Pliny, of a tree in the garden of Lucullus, which was so grafted 

 as to bear pears, apples, figs, plums, olives, almonds, grapes, &c. ; 

 and at the present time the gardeners of Italy sell plants of 

 Jasmines, Roses, Honeysuckles, &c., all growing together from a 

 stock of Orange, or Myrtle, or Pomegranate, on which they say 

 they are grafted. But this is a mere cheat ; the fact being, 

 that the stock has its centre bored out, so as to be made into a 

 hollow cylinder, through which the stems of Jasmines and other 

 flexible plants are easily made to pass, their roots intermingling 

 with those of the stock. After growing for a time, the in- 

 crease in the diameter of the stems thus enclosed forces them 

 together, and they assume all the appearances of being united. 

 Such plants are, of course, very short-lived. 



353. It may be useful here briefly to retrace the mode, in 

 which the elaborated sap is prepared and circulated. The roots 

 (or, failing them, the general surface of the plant, especially the 

 leaves and young bark) absorb fluid, which consists of water, 

 usually having some carbonic acid and ammonia diffused through 

 it, and also containing a small proportion of earthy matter 

 (. 169). This fluid is conveyed to the leaves, in part by the 

 attraction which they have for it, and in part by the propelling 

 force of the roots (. 116). Whilst ascending the stem, it is 

 mixed with some of the fluid previously elaborated, and it under- 

 goes some changes, in which oxygen is set free, and in which the 

 quantity of gum and sugar contained in it is increased. In the 

 leaves, a large quantity of superfluous fluid is parted with, by 

 exhalation and simple evaporation ; and a great deal of additional 

 carbon is obtained by the green surfaces, from the carbonic acid 



