PEUBLExVlS OF PROPAGATION. 



The extension here is into the air, but it is of the same character. 

 There is dying off behind of old parts in the heart of the tree and in 

 the bark that is shed, but a support remains for the copious canopy of 

 branches and leaves. Of the great age reached by some trees we are 

 all cognizant. 



There is, then, in the constitution of the plant everything con- 

 ducing to perpetuation by a vegetative process. 



If we wish to utilize the organization of the plant for multiplication 

 of individuals it is from Nature herself that we must learn in the 

 matter of vegetative propagation, and all our practice must be based 

 upon and developed out of the principles that we see in operation in 

 Nature. 



Let us take a simple illustration in, say, the strawberry or a plant 

 like Saxifraga Brunoniana (fig. 150). Here long branches are sent out 

 trailing on or over the surface of the soil. The bud in the axil of each 

 small leaf on such a branch is nourished by the mother-plant at first. 

 Then the stimulus of moisture at the position of the bud where it 

 touches damp soil evokes the formation of roots below it, the bud shoots 

 out into a branch, absorbs food for itself by roots from the soil and 

 leaves from the air, and becomes an independent plant, ultimately losing 

 connexion with the mother-plant through withering and breakage oi the 

 linking portion of branch. In this we have a process of normal vegeta- 

 tive propagation in Nature — natural layering — and you will note these 

 conditions : 



(a) The young bud receives an ample food-supply from the mother- 

 plant until it has rooted itself. 



(b) The roots develop in response to the prolonged stimulus of 

 water and at the expense of food supplied by the mother. 



These two facts are primary. They underlie all vegetative propa- 

 gation. Vv'^ithout food-supply, without water, vegetative propagation is 

 impossible. The gardener has tO' secure the presence of both of these 

 if he is to succeed in any propagative venture. 



Features similar to those which I have cited are often seen in large 

 trees of which some of the branches have reached the ground. They 

 are still attached to the mother-plant, but at the point where they 

 touch the ground the stimulus of moisture induces the development of 

 roots, and the end of the branch above this point is in fact an 

 I independent tree. The noted beech at Newbattle, and the remarkable 

 I specimens of Norway spruce at The Whim, in Peeblesshire, are con- 

 I spicuous examples. , What in the tree is usually • self -extension in 

 I branching here becomes self -propagation, and the tree imitates the 

 j condition of many herbaceous plants. 



1 In the strawberry and in Saxifraga Brunoniana and here in the 

 tree the mother-plant does not part with the young offspring until the 

 ! latter is self-established. 



1 But see what happens in Dentaria hulbifera (fig. 151). In the leaf- 

 \ axils there are the so-called ' ' bulblets. ' ' , What are they ? Merely buds 

 I m which some scale-leaves have enlarged as stores of food-material, and 

 VOL. XXXVIII. a a 



