PHYSIOLOGY OF TREES. 265 



Stem, according to the kind or peculiar structure 

 of the plant; — on every part of the trunk and 

 branches, as the myrtle ; and at the nodes only, 

 as the grape-vine. 



These gems mostly remain dormant, though 

 all of them may be prompted into action accord- 

 ing to the circumstances of position or extraor- 

 dinary impulses of constitutional vigour, espe- 

 cially if the stem be damaged, or cut over, im- 

 mediately above their station ; in which case they 

 will burst through the bark, or occasionally may 

 be seen issuing from the protruding cambium, 

 oozing out round the last year's alburnum at the 

 top. 



These facts are quite apparent to the most 

 careless observer ; and shew to a certainty the 

 seat of vitality, whence proceed all the incre- 

 ments of the vegetable being. The only diffi- 

 culty lies in conceiving how infinite gradations 

 of matter can previously exist in finite space ; 

 how innumerable folds of bark and wood can be 

 produced from a layer scarcely perceptible during 

 the winter half-year. Still it is an unquestionable 



