Chap. II.] 
COURSE OF THE SAP. 
55 
the case; the roots remain alive, and shoot out 
without any assistance from the atmosphere, 
and the heads immediate^ die. 
If leaves are picked, they will die sooner than 
if the bough is cut on which they stand; if 
the bough is cut, they will fade sooner than if 
the stem is cut on which the bough stands; and 
if the stem is cut, they will fade sooner than if 
the tree is grubbed. All this shows that the 
leaf is fed from the stem, and contradicts Lie¬ 
big’s notion, that leaves feed themselves and their 
parent trees from the atmosphere. 
Cut a branch in a hot sun in June or July. 
In a few minutes its leaves will fade, dry, and 
shrivel. What keeps their living brethren fresh 
and succulent through the fifteen hours’ drought 
and heat of our midsummer sun ? A constant 
supply of sap from the roots. If, indeed, a 
drought in summer or autumn is continued so 
long as to deprive the roots of moisture, the 
leaves will begin to fade; but the leaves will 
recover immediately, if the roots only are 
watered. Doubtless, if the leaves also are 
watered, and wetted hay-bands applied to the 
stems, it will expedite matters. For doubtless 
plants absorb from all parts which are exposed 
to moisture, and excrete, that is, transpire, or 
E 4 
