Retrospective Criticism. 521 



powerful effect in causing them to root. Those that have stood months, 

 without appearance of rooting, will strike in a few days in a strong heat. 



"601. Cuttings of the underground stems and roots. A great many plants, 

 both ligneous and herbaceous, may be propagated by cuttings of the under- 

 ground stems, as in the liquorice ; and of the roots, as in the common thorn, 

 and most of the Rosacea?." 



The best mark for such as strike most readily by pieces of the root is 

 an abundance of thick viscid juice, as in the genera -Rhus, Papaver, Aildntus, 

 Gymnocladus, &c, which strike more freely than Cydonia, roses, &c, which 

 have less. 



" 645. The uses of grafting. 3. To increase the vigour or the hardiness of 

 delicate species or varieties, by grafting them on robust stocks, such as the 

 Mexican oaks on the common oak, the China roses on the common dog-rose, 

 the double yellow rose on the China or musk rose, the Frontignan grape on 

 the Syrian, &c. 



"5. To increase the fruitfulness and precocity of trees. The effects pro- 

 duced upon the growth and produce of a tree by grafting, Knight observes, 

 ' are similar to those which occur when the descent of the sap is impeded 

 by a ligature, or by the destruction of a circle of bark. The disposition in 

 young trees to produce and nourish blossom-buds and fruit is increased by 

 this apparent obstruction of the descending sap ; and the fruit of such young 

 trees ripens, I think, somewhat earlier than upon other young trees of the 

 same age which grow upon stocks of their own species; but the growth and 

 vigour of the tree, and its power to nourish a succession of heavy crops, are 

 diminished, apparently by the stagnation, in the branches and stock, of a 

 portion of that sap which in a tree growing upon its own stem, or upon 

 a stock of its own species, would descend to nourish and promote the 

 extension of the roots.' " 



These modifications are, by stunting or lessening vigour of growth, to have 

 the wood better ripened, and the juices more highly organised or elaborated. 



" 650. Grafting by detached scions." It is of great consequence that the 

 graft and stock should be pressed closely together, in order that the first 

 emission of cambium from the stock should come in contact immediately with 

 the inner bark and albumen of the graft. When grafts are taken off, and 

 tied on in a growing state, the wood of the graft clings and dries ; having no 

 roots to feed it, it shrinks from the stock, leaving an empty space, and before 

 it is filled up, unless the stock is very vigorous, the graft dies. This might 

 be obviated by grafting before the sap rises, but grafts will not succeed till 

 the flow of sap has begun to rise briskly ; late grafting always succeeds best ; 

 and, hence, the grafts when taken off before growth commences, and kept moist 

 till the stock begins to grow, always succeed best, as they experience no 

 checks. Much of the success of grafting, however, depends on the state of the 

 weather; if the heat prevails so as to keep the sap flowing, every healthy 

 graft, well fitted, will succeed; if not, they may perish before the sap rises. 



" 669. Bud-grafting." A species of grafting I think you have not noticed 

 may be denominated bud-grafting, and is the best for most evergreens, as 

 daphnes, &c. When the stock has begun to grow vigorously cut the head 

 off, and, making an incision in the bark a few inches down, open it on both 

 sides, the same as for budding ; prepare the graft without a tongue, and insert 

 the lower part as you would do a bud, leaving the herbaceous growing top 

 green above. Soft succulent evergreens in which the bark opens freely will do 

 better in this way than any other. 



" 674. Budding. In the year 1824 we placed several buds on the branches 

 of a fig-tree, and, from some accidental cause, though the shield adhered in 

 every case, yet most of the visible buds were destroyed, and only one of the 

 latent buds was developed. Twelve years afterwards, when the fig-tree re- 

 ceived a severe check, in the winter of 1837-8, the developement of a second 

 latent bud from one of the shields took place." 



Were the buds developed latent or generated ? This will be difficult to decide - 



