The Descent of the Sap 



leaves ! Fluids distend the cells, ooze from 

 one to another, transpire, circulate and 

 exchange their matter in solution ; vapour 

 is emitted, gases come and go ; the sunlight 

 divides some substances and unites others, 

 and the raw components of the ascending sap 

 are formed into the material of life. 



The perfected sap descends from the leaves 

 to the twigs, from the twigs to the branches, 

 from the branches to the stem and thence to 

 the roots — being distributed in every direction 

 during its course. It circulates between the 

 wood and the bark. At the time when it is 

 most abundant, in spring, it forms a thin 

 layer of sticky matter between the wood 

 and the bark, so that the latter is easily 

 stripped from the branch. 



It is perfectly easy to note its downward 

 progress. If a ring of bark is removed from 

 a trunk the nourishing fluid will ooze out and 

 collect on the upper edge of the wound ; but 

 nothing of the kind is seen on the lower one. 

 When thus arrested by the interruption of its 

 regular path, the sap accumulates above the 

 bare ring and results in an abundant growth 

 of wood and bark, which is shown in a thick 

 circular swelling, while the trunk below the 

 ring retains its original dimensions. 



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