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XXXIV. On the Propagation of Trees by Cuttings in Summer. 

 By Thomas Andrew Knight, Esq. F.R.S., President. 



Read April 3, 1838. 



When a cutting of any deciduous tree is planted in Autumn, or 

 Winter, or Spring, it contains within it a portion of the true, as 

 it has been called, or vital sap of the tree of which it once formed 

 a part. This fluid, relatively to plants, is very closely analogous to 

 the arterial blood of animals ; and I shall therefore, to distinguish it 

 from the watery fluid, which rises abundantly through the alburnum, 

 call it the arterial sap of the tree. Cuttings of some species of 

 trees very freely emit roots and leaves ; whilst others usually pro- 

 duce a few leaves only and then die ; and others scarcely exhibit 

 any signs of life : but no cutting ever possesses the power of regene- 

 rating, and adding to itself vitally, a single particle of matter, till it 

 has acquired mature and efficient foliage. A part of the arterial 

 sap previously in the cutting, assumes an organic solid form ; and 

 the cutting in consequence, necessarily becomes, to some extent, 

 exhausted. 



Summer cuttings possess the advantage of having mature and 

 efficient foliage, but such foliage is easily injured or destroyed, 

 and if it be not carefully and skilfully managed, it dies. These 

 cuttings (such as I have usually seen employed) have some mature 

 and efficient foliage and other foliage, which is young and growing, 

 and consequently two distinct processes are going on at the same 

 time within them, which operate in opposition to each other. By 

 the mature leaves, carbon, under the influence of light, is taken up 

 from the surrounding atmosphere, and arterial sap is generated. The 



