GROWTH OF TREES. 24,3 



and no part of botanical phy«iology is more worthy a minute 

 inquiry. It is an easy matter to establish a beautiful theory to Necessary 

 captivate the imagination, though without elucidating a single '"^""^ o^ 

 fact : but to understand every part of the formation of a plant, 

 interior as well as exterior ; to dissect and watch its various 

 states and changes ; to examine thoroughly how it passes into 

 each, and what has been the general effect produced in the ve- 

 getable by such alterations ; to collect by dissection and by cul- 

 ture its habits and powers — these are the requisites, and all 

 this must be gained by examination and study, before we can 

 at last form a theory founded on truth, and learn to know 

 what a plant really is. This is my aim, and upon this I have 

 already employed fourteen years of the most unremitted appli- 

 cation. I shall now show the manner of a tree's increase in 

 every way ; how the spring and autumn shoots are protruded j 

 what is the difference of various trees in this respect, and also 

 the changes produced in the new shoot, when compared with 

 the older parts of the tree ; how the yearly stripe in the wood 

 is contrived, with many other particulars, as they may occur to 

 me. 



If a tree be examined about the beginning of August, it will The screws 

 be perceived, that a 'sort of screw is forming at the end of the which indicate 

 last year's shoot. Each different tree has its own peculiar screw, ^ ^ ^ ^oots. 

 appertaining to the whole genus. Thus, in the poplar it is long 

 and scattered ; in the oak, short and close. It is found by many 

 deep rims, which are partly the outward marks indicating the 

 bud, but perfectly divided all across the plant, one from the 

 other, within as well as without. When you take off the bark 

 and rind from the screw, you find the interior wood swelled 

 with the buds of the year, which are to develop the next 

 spring, and will then be arranged and placed in the bark of the 

 screw. It is now that you see, in the most pointed manner, all 

 I have before shown respecting the buds; viz. that the wood 

 vessels open and disperse to let them out 3 that the buds possess 

 all this time no other covering than a few coats of alburnum, 

 and have no scales till they reach their cradles in the ijrirk ; and 

 that it is the thickened form of this bark in each screw, which 

 allows of the concealment of the buds, wheTe they remain till 

 they have woven their scales or winter covering, I hjve said, 

 that the screw is a collection of rings or links j there is also 

 R 2 a part 



