314 PROPAGATION OF PLANTS. 



materials than can be used, there must ensue a forced, 

 unhealthy growth, or an entire inaction, in some part of 

 the plant. When a tree or shrub is severely headed back, 

 for grafting or other purposes, and thus deprived of its 

 usual amount of foliage, it will often expend the greater 

 part of its vitality in producing suckers or sprouts from 

 the base of its stem. No root wiU remain dormant and 

 healthy for any considerable time under circumstances 

 which are naturally favorable for promoting growth, and, 

 knowing this, the grafter should avoid cutting o£E all the 

 branches of a large tree at one time, unless he can substi- 

 tute a sufficient number of cions to fill their place, or at 

 least enough to allow all the roots to act, even if it be but 

 slowly. To avoid the too severe checking of root action, 

 it is better to graft only a part of the branches of large 

 trees one season, leaving the remainder until the next. 



Veneee Geafting. — This mode of grafting is princi- 

 pally employed in propagating woody plants under glass, 

 where both the temperature and hygrometric condition 

 of the atmosphere can be readily controlled by the propa- 

 gator. The usual time for performing the operation is in 

 summer, and soon after the first and most vigorous growth 

 of the season is completed, but before the wood and leaves 

 are fully mature. As the leaves on both stock and cion 

 are retained, they should not have entirely ceased to 

 assimilate sap at the time of grafting, but still remain 

 fresh and capable of performing all of their natural func- 

 tions. The time for performing the operation must neces- 

 sarily vary with different kinds, according to the differ- 

 ence in the natural habits of the various species, us some 

 make their growth much earlier in the season than others, 

 but the method of grafting is the same in all. 



In this mode of grafting the stocks should be grown 

 in pots for convenience in handling when performing the 

 operation, as well as afterwards, for the union between 

 stock and cion must be secured before the plants are re- 



