AND SUBORDINATION. 87 



from the cells of the cambium region. It is a fact well known 

 to gardeners, that under the influence of heat and moisture, 

 the leaves of Bryophyllum calycinum, Gloxinia, Gesneria, &c., 

 may be made to produce buds ; and the production of buds on 

 true roots has been frequently observed in Pyrus Japonica, 

 Madura aurantiaca, and Paulonia imperialis. Portions of the 

 roots of these plants, in a healthy condition, may be made to 

 produce new plants. Hence, in the case of willows and other 

 trees, whose tops have been removed, "it is not always easy to 

 decide, without dissection, whether the buds are really adven- 

 titious, or merely latent axillary buds stimulated into develep- 

 ment."* 



Buds are always formed from the cellular portion of the 

 stem, and in normal cases they may be distinctly traced on 

 young branches to the pith or medullary rays. This fact is 

 illustrated by the dark lines drawn through the centre of the 

 conical ramifications -of the diagram on page 59, which repre- 

 sents the pith in the centre of the branch and its branchlets, 

 and shows its connection with their buds or developing points. 

 In those cases where a bud has been formed by a leaf which 

 has died years ago, and has maintained its position on the 

 exterior bark in a latent condition, if a section be made at the 

 point of the stem where it is seen to protrude, the vegetative 

 course of the bud will be marked by a line of pith called the 

 wake of the bud, which traverses the several layers from the 

 centre outward.f It follows from this, that branches of the 

 same age mav have originated from buds which have been 



O J O 



formed at different periods of the life of the tree. Hence, as 

 growth progresses, and the successive conical layers accumu- 

 late year after year around the stem and its branches, the 

 original points of development from whence the first vitally 

 active buds proceeded, become deeply seated in the interior of 

 the stem ; for the wood of the principal branches of the tree 

 which usually developes from the earliest vitally active buds, 



* An Elementary Course of Botany, Structural, Physiological, and Sys- 

 tematic, by ARTHUR HENFEY, page 69. 



f See article " Botany," in Lardner's Cabinet Cyclopaedia. 



