THE SOUTHERN PLANTER. 



9 



settle in winter, into the roots! One 

 would have thought that the notorious 

 difficulty of cramming a quart of water 

 into a pint measure, might have suggested 

 the improbability of such a phenomenon. 

 For it certainly does require a very large 

 amount of credulity to believe that the 

 fluids of the trunk and head of a tree 

 can, by any natural force of compression, 

 be compelled to enter so narrow a lodging 

 as the root. The idea, however, has es- 

 tablished itself in some persons' minds, 

 and, we presume, in connexion with that 

 other old vulgar error, that the sap is in 

 rapid motion in the spring time, in the 

 roots of a tree, before it begins to flow in 

 the branches. 



We shall assume the word sap to sig- 

 nify the fluids, of whatever nature, which 

 are contained in the interior of a tree. In 

 the spring this sap runs out of the trunk, 

 when it is wounded ; in the summer, au- 

 tumn, and winter it does not, unless ex- 

 ceptionably, make its appearance. But 

 in truth, that sap is always in motion, at 

 all seasons and under all circumstances, 

 except in the presence of intense cold. — 

 The difference is, that there is a great 

 deal more of it in the spring, and much 

 less at other seasons. 



When a tree falls to rest at the approach 

 of winter, its leaves have carried off so j 

 much more fluid than the roots have been 

 able to supply, that the whole of the in- 

 terior is in a state of comparative dryness, ! 

 and a large portion of that sap which J 

 once was fluid, has become solid in con- 

 sequence of the various chemical changes j 

 it has undergone. Between simple eva- ! 

 poration on the one hand, and chemical 

 solicitation on the other, the sap is in the' 

 autumn so much diminished in quantity, j 

 as to be no longer discoverable by mere 

 incisions. The power that a plant may 

 possess of resisting cold, is in proportion 

 to the completeness of this drying process. ! 



When the leaves have fallen off, the 

 tree is no longer subject to much loss of 

 fluid by perspiration, nor to extensive che- \ 

 mical changes by assimilation, for the 

 leaves are the principal organs of perspi- 

 ration and assimilation. But the absorb- 

 ing power of the root is not arrested ; 



they, on the contrary, go on sucking fluid 

 from the soil, and driving it upwards into 

 the system. The effect of this is, that 

 after some months of such an action, that 

 loss of fluid which the tree had sustained 

 in autumn b}' its leaves, is made good, and 

 the whole fabric of the plant is distended 

 with watery particles. This is a most 

 wise provision, in order to insure abundant 

 food to the new-born leaves and branches, 

 when the warmth and light stimulate 

 them into growth. 



During- all the winter period, the sap 

 appears indeed to be at rest, for the re- 

 filling process is a very gradual one. But 

 M. Biot, many years ago, proved, by an 

 ingenious apparatus, that the rate of mo- 

 tion of sap may be measured at all sea- 

 sons ; and he ascertained it to be in a 

 state of considerable activity in midwinter. 

 Among other things, he found that frost 

 had considerable influence upon the direc- 

 tion in which the sap moves. In mild 

 weather, the sap was constantly rising ; 

 but when frost was experienced, the sap 

 flowed back again — a phenomenon which 

 he referred to the contracting influence of 

 cold on the vessels of the trunk and 

 branches, the effect of which was to force 

 the sap downwards into the roots, lying 

 in a warmer medium ; then, again, when 

 the frost reached the roots themselves, and 

 began acting on them, the sap was forced 

 back into the trunk ; but as soon as a 

 thaw came on, and the ground recovered 

 its heat, the roots out of which a part of 

 the sap had been forced upwards, were 

 again filled by the fluids above them, and 

 the sap was forced to fall. A large poplar 

 tree in the latter state, having been sawed 

 across at the ground line, the surface of 

 the stump was found to be dry, but the 

 end of the trunk itself dripped with sap. 

 Sap, then, is always in motion ; and if it 

 ever settles to the roots in a visible man- 

 ner, that is owing to external temporary 

 causes, the removal of which secures its 

 instant re-ascent. 



As to the idea that the bleeding of a 

 tree begins first at the root, and, in con- 

 nexion with this supposition, that what is 

 called the rise of the sap is the cause of 

 the expansion of buds, and leaves, and 



