Propagation of Plants hy Cuttings. 127 



being produced in the interior of plants. The vital principle 

 seems to guide and direct the various combinations that the 

 simple elements which they absorb, undergoes within their 

 vessels. But the process by which the elaborated sap is con- 

 verted into cellular tissue, or any other form of vegetable 

 structure, or the mode in which water and carbonic acid are 

 changed into gum or sugar, is, and may for ever remain a 

 profound mystery. 



From the view I have taken of the subject in question, I 

 am led to the conclusion, that the callosity formed on the 

 base of a cutting, is produced by the aqueous matter which 

 it absorbs from the soil, mingling with the stored-up sap, and 

 undergoing a change in the interior of the shoot, analagous, 

 probably, to that carried on in the germination of a seed.* 

 Judging from the external appearance of this accumulated 

 matter, some such combination appears likely, as it is appa- 

 rently a mass of imperfectly organized woody fibre. As it 

 extends, it takes the appearance and performs the functions 

 of a spongiole, and gradually becomes converted into true 

 woody fibre, as the cutting increases in growth. 



It is not to be inferred from the above, that the whole of 

 the leaves ought always to be removed from cuttings ; this, 

 in the majority of cases, would be positively injurious ; but 

 I think it sufficiently clear, that the leaves perform no active 

 part in the first formation of roots ; consequently they ought 

 not to be excited into growth, but placed in the lowest aver- 

 age temperature consistent with the nature of the plant, 

 while the soil in which they are inserted should approach 

 the highest range of temperature the roots will endure ,* to 

 stimulate into activity the processes carried on in the vessels 

 beneath the surface of the soil. And the more completely the 

 upward growth of the cutting is retarded, until rootlets are 

 formed, the greater chance has the cutting to thrive. 



* Diastase is always present in tlie germination of seeds. The willow contains a large 

 quantity of starch among its woody fibre, and cuttings if it emit roots freely. May not 

 diastase be formed at the base of the cutting, to transform the starch and render it solu- 

 ble and Cited for facilitating the emission of roots ? And may we not form an idea of 

 the facility with which cuttings strike root, by the amount of starch contained in their 

 structure ? 



