Telegram-herald., 1889-11-20
WAY LEAVES FALL.
C4ri0Gs Fzcts Kelatias - tbs HABITS
Plat Life "a S2rt01s CliEaes-

I4rtoGs tActs Eel4tt2s - the hAcits .
Plat Life "a N&rto1s CliEaes-
y wo-lt. perhaps. seen - 20 almost
without saying that the reason Wy -
imzls and plants retire into snug quar-
ters and sleep through the winter. and
Why tAo trees and shrubs c4s1 on their
tender leaves Ia sutumn, IS because Ia
this nay they avoid the serious injury
which would come from exposure % The
extreme cold. Moreover, II Is we'll
known that as Ne approach the tropics
the plants are found 70 remain in leaf
later and later, and some OF the very
kinds that with Us are leAfess for many
months are, in those regions OF uniform
warmth. fully provided With foliage the
year round Thus peach trees IN the
northern part Of Africa are reported 70
retain their leaves through the winter,
and in me spring TO produce flowers on
the leafy branches.
BIT an tropical regions DO not present
such nniform conditions OF moisture.
saws tia Boston Transcript; on the con
trary. there is In many places = we'll
marked division Of the year into a dry
season, when tho air is very hot, and
wet season, which is decidedly cooler.
Now, travellers tell Us that vegetation in
such climates is active only during the
Wet season, and at the approach OF the
dry and hotter period the leaves fall of,
animals burrow in the earth and be-
come dormant, and all life-aDimal and
egetable-behaves in q manner strik-
ingly similar 20 that with which We are
familiar in the land OF snow and ice.
Surely when increase OF heat is accom-
panied by the same sort OF changes as
increase of cold something besides mere
temperature must be concerned.
AS 10 what this something may be ws
have a hint from the fact just mentioned
that the hotter season in the tropics is
at the same time much drier, and there
is no reason 10 believe that the plants
would suffer from the increase OF heat
ifthey had all the moisture they needed.
Hence IL is clear that the leaves are
shed, not so much 10 escape heat as TO
avoid draining the plant of necessary
moisture that could not be replaced.
Still il is not so obvious how lack OF
moisture can account for the shedding
of leaves in our colder climate, for our
rainfall, at least in the form of snow, is
about as much in winter "a in summer.
We have only to remember, however,
that moisture in this form can no more
be absorbed by the roots of plants than
can the dry sands OF the desert, as it is
plain TO be seen that Just as absence OF
moisture is the chief thing to be feared
- IN Crrr rrrrir, ,-or
is the impossibility of using the moist
ure at hand In short, we see from this
that irreparable loss of moisture is the
real danger against which plants are
protected alike by their summer sleep
in the tropics, and their winter sleep in
colder regions.
Not that other important ends are not
accomplished at the same time. Every
one can see that tree bearing broad
leaves would suffer greatly from such a
; burden ot snow as would be heaped upon
il in severe storm, while the amount
that could lodge upon its naked branches
would be comparatively insignificant.
Then there is another advantage which
comes from the fact that at the end of a
seasons activity every leaf is found TO
be more or less encumbered with tho
waste products of plant work. These
would decidedly interfere with the fut-
ure work Of the organ could it be re-
tanned; so it is good thing for the plant
10 be freed from these harmful sub
stances, even though the leaf be sacri-
feed at the same time. As it IS, how
ever, there is very little OF value cast
away-scarcely more tsan an old frame
work filed with the substance above re.
ferred tO-fOr. as shown by careful ex-
periments, the precious living matter OF
tho leaf, and the sugar, oil and other
food stufs IL has made. retire into tho
stem. whence they issue in the spring
as formers of the expanding buds. Even
the parts which fall are not wholly lost
70 the plant, but help to nourish it by
their decay and mingl,ng with the earth.
Tho sacrifice, IL sacrifice il be, is made
deliberately, for not only is the loss re-
duced as much as possible by the with
drawal OF all that is most valuable in
the leaf. but special provision is made
( 20 have clean, well-pro.ected wound
This is accomplished by the formation
Of layer Of cork directly across tho
base of the leaf, and what could be bet
ter than cork where the need is for a
material which shall h-eak apart easily
and leave a smooth. water proof surface?
r has been we'll said that here is a case
Of self-amputation, where tho wound Is
made and healed before the limb falls
or Several weeks nay be occupied in
tho making 81 the layer. SO that indica-
tions OF its appearance are often 70 10
found early in the autumn. and We must
therefore consider 10 as formed in an
ticipaton or the costs rather than in
+ response 70 them.
Although 10 may be- admitted that cold
has not tho Importance commonly as
signed % it as the cause Of leaffalL
those who have noticed how rapidly the
leaves drop Ist after still. cold night
might we'll point out that a. loast Tho
frost vas effective in giving 'he final
push Perhaps this may he true. Tor it
can not BE- denied that sudden froezing
would tend 90 make tho cork plane brit
tle, hgt on tho other hand. So would the
Sudden drying which coraes vifh sharp
frost, and tho sad3en warm nx hy the
morning sun nav help 20 rond the deli
cs'e tissues by produr.ng irregulsr eS-
pansion. A. any rst~. I'm view of thesN