The Pickens sentinel. [volume] (Pickens, S.C.) 1871-1903, 1882-11-23
Dead BranChes Detrimental.

have been asked whether the state
ment now going the rounds of tho pa
pers that "a dead branch on a tree
makes almost as great q strain on the
main plant for moisture as does living
one" is accurate or not. The statement
Is coupled with another referring to its
practical application in tree culture, the
conclusion being that every dead
branch "should be at once cut away.h
Briefly it might be answered that the
first statement is true in the main, and
that, without any doubt at all, the con
clusion is wise one and ought to he
followed in practice. TO explain this
matter will take considerable more
space, and in order to understand it we
must 60 to vegetable physiology and in
quire into the nature of the evaporation
OF water from plants. 1t was long sup
posed to he physiological process, and
was considered to be entirely different
from ordinary physical evaporation. AS
long as this view was held the process
was called Transportation, to distinguish
it from the physical process Tho
breathing pores, the stomata, which oc-
cur in the epidermis of all leaves in
| great numbers, were supposed to be
organs Of Transportation, which was con-
| sidered to be one of the most important
| functions of the leaf.
| Within few years, however, our
| knowledge of these matters has been
| greatly increased and we now know that
the escape OF water from the leaf does
not dillec in any way from the evapora-
| ton OF water from any other moist sur
face. A leaf is q mass of coils, cverv
| one of which is gorged with watcry mat
ter, which in dry atmosphere, as q
matter OF course, tendE to escape. The
| eplderms, composed of dryish, impervi-
Gus cells, which entirely surrounds the
watery cells of the leaf. would prevent
almost completely the evaporation of
water from the latter were it not for tho
! breathing pores before mentioned.
| These pores are for permitting the free
ilngress and egress of gases, particular
| ~ oxygen, carbonic acid and probably,
also, ammonia. Now, when the pores
are open for their legitimate purpose it
happens that more or less water es-
capes, if the air is dry. If the mir hap
pens to be very moist the loss Of water
through the breathing pores is very lit
tie or even none at all.
We may put it in this way: the leaf
! loses water simply because it is q watery
| structure; its cpdermis is designed to
prevent this loss, and the breathing
! pores with their power of opening and
! closing are for the same purpose. A
leaf instead Of being an organ Of evap-
Grafton is actually u structure in which
. evaporation is quite successfully
checked. Careful experiments made
under my supervision in the Iowa Agri-
cultural College in 1880 by Miss Ida
Twtchcll, II graduate student, demon
stratcd that the evaporation from q
moist piece of dead wood was exactly
! like that from living leaf. Now when
n dead branch is large enough to keep
continually moist in the interior it will
! in dry air constantly lose water by evap-
oration from its surface. This water so
lost is taken from the tree, and must
/ have been supplied directly or Indirect
ly by the living portions. Moreover, it
! must be remembered that living
! branch is well protected against loss Of
! water through evaporation, by the cpl
! dermls which covers all its surface when
young, or the imperN ious corky bark
which is always found on it when older
When branch dies, these protecting
de'iccs soon fall into decay and the wa.
ter, so carefully guarded by the living
parts of the plant, is wasted by evapo.
ration-PcOt. BcSScM IN A. \, IriJU1lG