272 



TRANSACTIONS OF THE 



THE COURSE OF THE SAP. 



To observe this beautiful process I cut a small tree down near the ground, 

 and thrust it into a vessel of prepared madder, which in a few minutes as- 

 cended through the capillary tubes of the tree, and not only tinged them, 

 but even the leaves were sensibly affected, after which the return sap col- 

 ored the bark. This shows plainly, that the sap from the roots passes 

 through the tubes in the wood, by capillary attraction, to the leaves, over 

 which it spreads itself, and then descends again through the bark, and passes 

 off at the roots' extremities. 



Of the the importance of leaves in the economy of vegetation, I once had 

 sufficient proof. A new gardener stripped all the leaves from a few grape 

 vines that were in full bearing, and the result was total destruction of the 

 fruit. On another occasion early frost destroyed the leaves of some peach 

 trees that were full of fruit, and the result was entire loss of crop. Mil- 

 dew attacked the leaves of a small quince plantation, and deterioration of 

 the fruit followed. 



The functions of the stems of plants are as various as those connected 

 with the roots, and they appear to possess the same discriminating power 

 of admitting into their circulation the numerous substances in the soil. I 

 found that the trunks of some trees which I thrust into the liquid madder, 

 rejected it entirely, in the spring of the year, but accepted it readily in the 

 fall. How will physiologists explain this ? I suppose the reason is that 

 the sap flows less rapidly in the fall than spring, and confines itself more to 

 the internal part of the tree, consequently I never attempt to impregnate 

 wood with kyanizing solutions, except in the autumn. The pine, :ind I 

 imagine all other evergreens, circulate sap throughout the year, as by ex- 

 periment I find they will receive liquid coloring solutions, or salt, at any 

 time. 



You may always discover the age of a tree, by examining the zones an- 

 nually formed. Though this has been denied by a learned man belonging 

 to this Institute, I am convinced, after making one hundred experiments, 

 that it is true. The zone formed the first year around the pith, consists 

 entirely of wood}' fibre, firm on the exterior, but intermixed with rays on 

 the interior, tending towards the centre. The following season, another 

 similar zone is formed, which does not undergo any alteration of structure 

 afterwards, and always remains as long as the tree lives to mark its age. 

 The formation of the wood of a tree, is entirely difi"erent from that of the 

 bark ; the latter grows by addition to its internal economy, and the former 

 by deposits upon its external. 



There are very many conditions requisite to sustain the life of plants, 

 and besides those of each genus, require without a doubt, special condi- 

 tions, and if by any accident one of these is entirely deficient, though all 

 the rest are present, the plant will fail to mature. 



How then shall we restore fertility to our sods, and fit them for the re- 

 ception and germination of the seed ? 



