420 Mr. Colvill on the Origin of Buds. 



to illustrate his views, relates the case of an elm tree which had been wounded by 

 decortication. On the edges of this wound was formed a lip of new bark and wood, 

 whose surface was marked with ridges and furrows indicating a growth of at least 

 three years ; and from the last and innermost ridge there had issued two shoots 

 of several inches in length, in the course of the preceding summer. The au- 

 thor infers that these shoots could not have originated in, nor proceeded from the 

 pith or centre layers of wood, because the vitality of the outer layer had been de- 

 stroyed by means of its exposure to the atmosphere, in consequence of the decor- 

 tication of part of the trunk, so that it could no longer afford a passage for a 

 centrifrugal band. Further, on dissection he found that the buds had no radi- 

 ant nor radical connection with the centre of the stem, a layer of doad wood in- 

 tervening, to which the bark and wood of the lip were indeed vegetably agglutina- 

 ted, but not connected by a continuity of living growth. Beyond that layer the 

 medullary rays began anew and took a totally different direction. " Hence," 

 Mr. Keith remarks, " it follows irresistibly, that the shoots in question originated 

 merely in the lip, and sprung from buds, which, if not formed by, were yet con- 

 veyed to, and deposited in the alburnum through the medium or agency of the 

 proper juice, without having ever been connected with the pith or central layer 

 of the incipient stem, and without having been annually protruded towards the 

 circumference through each successive layer of wood" ; in short, that *' a plant 

 may contain latent germs besides those which are annually carried outwards in a 

 horizontal direction ;" though the fact of their evolution must be viewed as an 

 exception to the general rule, rather than as an illustration of the law. 



As to the oriffin of buds, in cases where the horizontal progression of the germ 

 is impossible, Mr. Keith advances the theory that " the bud or buds already ex- 

 isting in the embryo plant have the power of generating new buds, which the plant 

 has the power of propelling to their appointed stations :" — " say that this process 

 is effected by the bud or buds lodged in the embryo plant, or protruding from the 

 surface of the shoot, and the new formed bud, or rudiment of a bud, a minute, and 

 insulated, and imperceptible globule or filament; there is nothing incredible in the 

 supposition of its being carried upwards with the current of the ascending sap in its 

 passage through the alburnum ; or, of its entering even the plexus of the vessels of 

 the inner bark, being again carried downwards with the current of the descending 

 and proper juice, as well as ultimately deposited in a situation favourable to its fu- 

 ture evolution." " Not," the author continues, " that the horizontal progression 

 of the bud, as a general rule, is to be denied. The fact is established beyond a 

 doubt. But that the exception to the rule must be accounted for also ; and even 

 upon the principle of the rule itself, I am not sure that the longitudinal progress 

 sion of the bud may not be occasionally wanted, if it were but to bring buds up 

 to the point of their horizontal protrusion." 



It will be interesting to compare the opinions of Mr. Keith with the ingenious 

 views contained in the preceding paper. From the talent for inquiry exhibited 

 by the author of this memoir, we consider it to be a duty which he owes to this 

 most important science, physiological botany, that he continue to pursue these 

 researches ; and we trust that we shall be again favoured with the fruits of his 

 " leisure hours." — Ed. 



• Phil. Mag. vol. xlv. 56. 



•f De la Terminaison des Plantes. 



