*with Hints for tlieir Removal. s$ 



growth of the tree, out of the very stones or sand (which Sir 

 Humphry Davy has proved to be perfectly barren), for the 

 support of not only the stem, but that oiFspring of " complete 

 bloodsuckers," as Mr. Howden terms the branches and leaves. 



If any able chemist can satisfactorily prove by analysis 

 that the very rocks, sand, or sandstone, where such trees are 

 found to grow, some in great luxuriance, contain all the 

 carbon and other ingredients that constitute the food of trees, 

 and form the sap, wood, and leaves, we might then be con- 

 vinced that leaves were of no use to imbibe any part of the 

 necessary food from the gases in the atmosphere : but how 

 they will reconcile the difference between such barren rocks 

 and sands, and the best of soils, I must confess I am at a 

 loss even to conjecture. 



Now, to the use of the branches and leaves in the increase 

 and growth of the wood or timber. In Lecture 3. (Vol. VIII. 

 p. 512.), on the formation of timber, Mr. Lindley says : — 

 " The timber is increased by concentric layers, formed one 

 every year between the inner bark and alburnum, or surface 

 of the young wood, the manner in which this layer is depo- 

 sited is the point where botanists do not agree." Of the 

 various opinions that have been broached on this subject, Mr. 

 Lindley said, he should only state two, which he considered 

 the principal. 



" First, That the increase in diameter of timber trees is 

 effected by the annual transformation of the inner bark into 

 alburnum, hardening into wood, and a new inner bark being 

 formed by the exudiiig juices of the tree." Perhaps Mr. 

 Howden's opinion, probably the candlemaking way. Se- 

 condly, " That fibres are constantly sent down by the leaves, 

 which, embedding themselves in the cellular tissue formed by 

 the descending sap, make a new layer between the inner bark 

 and the alburnum. Various experiments have been tried by 

 the supporters of the first of these opinions ; one of which 

 seemed almost conclusive,; _A portion of the outer bark 

 having been removed, and «a thin plate of silver having been 

 bound on the outside of the inner bark, this plate of silver 

 was buried in the tree." 



On the other hand, the advocates for the second hypo- 

 thesis, viz., that the layer of new wood is formed by deposi- 

 tions from the leaves, assert that, if a tree be ringed to such 

 a depth as to cut off the communication between the albur- 

 num and the leaves, the stem below that ring will not increase 

 in size ; but that the part above the division will exhibit an 

 extraordinary swell, as though the nourishment intended for 

 the whole trunk were concentrated to that point. In further 



E 4 



