4^ Mr. Colvill on the Circumstances under which Germs 



the pre-organized germs are deposited, so as to pervade the whole 

 of the plant, it is evident that the precautions here recommended 

 would be totally unnecessary, because these germs would exist, 

 and should consequently germinate equally above and below the 

 eye or joint. But in wood whose age is not such as to have totally 

 obliterated all traces of the eye upon the bark, it is seen that such 

 a result does not follow, but that the wood dies down to the next 

 joint or eye, at which, or in whose neighbourhood alone, the new 

 germ or bud is protruded. How far this new germ or bud is con- 

 nected with the joint or eye remains to be investigated. In the 

 meantime it appears that we are entitled to draw the conclusion, 

 that the pre-organized germs of Du Hamel do not pervade the 

 whole of the plant as he supposed. 



Another theory has been advanced by the acute author of the 

 article on Vegetable Physiology in the Library of Useful Know- 

 ledge.* Of all the theories this seems to agree most nearly with 

 the test of experience, although it is not by any means completely 

 satisfactory. At one part it would appear that the author meant 

 to distinguish betwixt a germ and a bud. " All branches," he 

 says, " proceed from germs, formed in the earliest unfolding of the 

 parts in which they appear, although the buds produced from these 

 germs may not be protruded until the tree be greatly advanced in 

 age." By the word germ, however, he evidently understands 

 merely the hud in a less advanced state ; for he afterwards says, 

 that the germ is " the lateral progeny of the plant, generated at 

 the period of the developement of the stem or the branch on which 

 it appears as a bud." In following out the present inquiry, there- 

 fore, I apprehend that there will be no inaccuracy in supposing that 

 germ and bud mean the same thing, viz. a bud in its different 

 stages of advancement."t 



. To explain this theory a little farther, I shall take the liberty of 

 quoting a few more passages. Speaking of the germ, he says that, 

 when it is neither destroyed nor unfolded into a perfect bud or 

 branch, it " will advance to the surface of the next year's belt of 

 wood, and so on progressivelv, or perish with the destruction of the 

 tree." He adds, that " no determinate period is fixed for the pro- 

 trusion of the germ into a bud ; but, at whatever time this may 

 happen, its course is traceable from the medullary sheath, to the 

 surface on which it appears, by a pale streak of parenchymatous 

 matter traversing each annual concentric ligneous layer." 



This theory accounts justly enough for the progress and produc- 

 tion of the buds formed upon a branch in the first year of its growth ; 

 but, on- subjecting it to the test of experience, it will be found to 

 be very far from affording a satisfactory explanation respecting the 



• Lib. of Useful Knowl. No. XIV. Chap. V.' 



"t" It must not be supposed that it is meant to object to this distinction, which 

 has been sanctioned by the most celebrated botanists, (Sir J. E. Smith, Sprengel, 

 &c.) but it is proper to point it out to prevent "misapprehension. 



