VEGETABLE PHYSIOLOGY. 23 



convenience to beauty and regularity being always preserved. 

 Nature has given different coverings to different vegetable 

 productions, according to the peculiarities of their respective 

 climates. In northern regions, the buds are almost universally 

 clothed with scales, or with a downy substance ; sometimes these 

 are conjoined, besides being coated with a resinous matter. 

 The horse chesnut and some of our walnuts are good illustrations 

 of large and well-formed buds. By means of these coverings, 

 the young bud is enaHed to brave the vicissitudes of the seasons, 

 and to be ready to burst forth on the first approach of spring. 

 This singular power of retaining its vitality, has been considered 

 by some physiologists as the distinctive character of true buds. 

 The most external of the scales are dry and hard, while those 

 that are more protected from the influences of the weather, are 

 soft and succulent. Take a bud, for instance, of the horse 

 chesnut, and close the part which has been just separated from 

 the stock with wax, plunge it into water, and it will remain there 

 without undergoing any alteration for a number of years. 



Tn mild, or even in warm countries, buds have no scales, as 

 they do not require them. Those trees that form an exception 

 to this observation, can thrive indifferently in ^any climate ; so 

 that the rule holds in all distinct cases. The scales are consid- 

 ered by many as imperfect leaves. 



The internal structure of buds is said not to differ, in any 

 respect from that of the plumule, previously to its being detached 

 from the seed. Some have fancied, that they have seen the 

 rudiments of every part of the tree concealed in the bud. We 

 are much inclined to question the accuracy of such very minute 

 observers, and, of course, are more willing to impute any errors 

 to optical deception, than any wish to mislead. 



The bark and the pith have generally been considered the 

 source of the buds ; but the ingenious experiments of Mr. Knight 

 have set aside both of the hypotheses, and have established, as 

 far as the present state of the science will permit, the doctrine, 

 that they derive their origin from the alburnous portion of the 

 tree. This gentleman first showed, that they do not originate in 

 the pith or bark ; and also, that Du Hamel's opinion of pre- 



