PROPAGATION OF VARIETIES. 17 



Plum, and ends with the Pear and Apple. The precise time of course 

 varies with the season and the climate, but is generally comprised from 

 February to the middle of April. The grape-vine, however, which 

 suffers by bleeding, is not usually grafted until it is in leaf. The most 

 favorable weather for grafting is a mild atmosphere with occasional 

 showers. 



The scions are generally selected previously, as it is found, in nearly 

 all kinds of grafting by scions, that success is more complete when the 

 stock upon which they are placed is a little more advanced the sap in a 

 more active state than in the scion. To secure this, we usually cut the 

 scions very early in the spring, during the winter, or even in the autumn, 

 burying their lower ends in the ground in a shaded place, or keeping 

 them in fine soil in the cellar till wanted for use. In cutting scions we 

 choose straight thrifty shoots of the last year's growth, which may remain 

 entire until we commence grafting, when they may be cut into scions of 

 three or four buds each. In selecting scions from old trees it is always 

 advisable to choose the most vigorous of the last year's shoots growing 

 near the centre or top of the tree. Scions from sickly and unhealthy 

 branches should be rejected, as they are apt to carry with them this feeble 

 and sickly state. Scions taken from the lower bearing branches will pro- 

 duce fruit soonest, but they will not afford trees of so handsome a shape 

 or so vigorous a growth as those taken from the thrifty upright shoots near 

 the centre or top of the tree. Nurserymen generally take their scions 

 from young grafted trees in the nursery-rows, these being usually in better 

 condition than those taken from old trees, not always in a healthy state. 



The stock for grafting upon is generally a tree which has been 

 standing, at least for a year previously, on the spot where it is grafted^ 

 as success is much less certain on newly moved trees. 



In the case, however, of very small trees or stocks, which are grafted 

 below the surface of the ground, as is frequently the practice with the 

 Apple in American nurseries, the stocks are grafted in the house in 

 winter, or early spring, put away carefully in a damp cellar, and planted 

 out in the spring ; but this method is only successful when the root is 

 small, and when the top of the stock is taken off, and the whole root is 

 devoted to supplying the graft with nourishment. 



The theory of grafting is based on the power of union between the 

 young tissues or organizable matter of growing wood. When the parts 

 are placed nicely in contact, the ascending sap of the stock passes into 

 and sustains life in the scion ; the buds of the latter, excited by this 

 supply of sap and the warmth of the season, begin to elaborate and send 

 down woody matter, which, passing through the newly granulated sub- 

 stance of the parts in contact, unites the graft firmly with the stock. 

 " If," says De Candolle, " the descending sap has only an incomplete 

 analogy with the wants of the stock, the latter does not thrive, though 

 the organic union may have taken place ; and if the analogy between the 

 albumen of stock and scion is wanting, the organic union does not ope- 

 rale, the scion cannot absorb the sap of the stock, and the graft fails." 



Grafting therefore is confined within certain limits. A scion from 

 one tree will not, from the want of affinity, succeed on every other tree,, 

 but only upon those to which it is allied. We are, in short, only success- 

 ful in budding or grafting where there is a close relationship and simi- 

 larity of structure between the stock and the scion. This is the cas& 

 with varieties of the same species which take most freely, as the different 



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