122 MASSACHUSETTS HORTICULTURAL SOCIETY. 



than those grafted in February and March ; these later ones 

 growing more to wood. The working of trailing varieties of 

 shrubs or trees on tall stocks makes the so-called weeping trees ; 

 for instance, the Camperdowu elm, weeping mulberry, cherry, salix, 

 Prunus Cliamcecerasus, and many others, which, on their own 

 roots are trailers or creepers. All sorts of variegated and cut- 

 leaved foliage trees are preserved and multiplied by grafting. It 

 is also employed to aid the healing up of wounds, by grafting on 

 them scions or strips of bark. 



Physiology of Grafting. — Grafting and budding are governed 

 by the same physiological principles. There must exist an affinity 

 between the stock and the scion or else there can be no permanent 

 union. 



The physiology of grafting is, that the shoots springing from the 

 buds of the scion become united to the stock by the newly gener- 

 ated tissue, which tissue, when once united, determines the ascent 

 of the sap, rising from the stock ; which sap, after being elaborated 

 into the true or proper juices by the leaves on the scion, descends 

 by the inner bark. The sap, however, must be sufficiently homo- 

 geneous {i. e., must be prepared in plants of the same family) to 

 be readily absorbed by the growing cellules, near which it passes. 

 Id other words, each cellule elaborates sap according to its own 

 nature, and if the ascending sap has only an incomplete analogy 

 with the wants of the scion, the latter does not thx'ive, though the 

 organic union between it and the stock may take place ; and if the 

 analogy between the alburnum of the stock and scion is wanting, 

 the organic union does not long continue. Hence, evergreen 

 scions seldom succeed for any length of time when grafted on 

 deciduous stocks, or the apple on the pear, or vice versa. Thus, 

 in a physiological view, the epochs of vegetation are the principal 

 points to be attended to, as no plant can be grafted on another 

 which does not thrive in the same temperature. Nor can two 

 plants in which the sap is not in motion at the same time be 

 successfully united. This is because it is only when cellular 

 tissue is in a state of activity — when it can form accretions — 

 that a vital union can be formed and maintained and a reciprocal 

 activity must exist in stock and scion for that purpose. No union 

 can take place between the parts of two plants previously formed, 

 except when both parts are in the act of forming the vital tissue, 

 union being effected only by the coalition of the newly generated 



