'Cbe Conservative * 9
hawthorn and others are largely distri-
j buted by wild animals which eat the
fruit and allow the seed to pass through
the alimentary canal uninjured or carry
off the fruit and spit out the seeds.
Many seeds or seed vessels have bur-like
or sticky coats by which they adhere to
animals and are thus carried consider
able distances. Very often bodies of
water aid in the distribution of seeds
since all that are spread by the agency
of the wind and most of those that have
fleshy coverings will float on the surface
of the water and may in this way be
scattered.
Different species of trees naturally
develop different shapes. Some , like
spruces , tamarack
CTT 4 T > 17ii . UI ? rPII'lTCl . . , .
jlllfi Balsam have a
decided tendency to form a strong stem
and to take on a conical form in prefer
ence to the development of a crown or
head while others like the basswood ,
oaks , maples and box elder develop their
crown in preference to their stem. The
actual shape of trees depends on the
space they have to grow in , on the soil ,
situation , and on the age of the trees.
Where trees have plenty of room to
grow , and their natural development is
not interfered with , their individual
characteristics are most apparent.
TREE GROWTH.
Plants are made up of various tissues
and these are formed of numerous cells.
The material ol
ASSIMILATION. whioh these cellfe
are composed is largely carbon. This car
bon is derived from the carbon dioxide
( carbonic acid ) of the air which enters
into the leaves and under the action of
light , air and water is there decomposed
the oxj'gon is given off and the carbon is
retained and combined with water obtained
tainod from the roots , forms starch
sugar , gum and other plant foods.
This process of food making is called
assimilation and can be earned on onlj
in the green parts of the plant and ii
these only when exposed to light and
air. Hence , foliage , air and light at tin
top are essential prerequisites for tre
growth and other conditions being fav
ornblo , the greater quantity and botte
development of foliage and the more
light this foilago has at its disposal for
its work , the more vigorously will the
tree grow.
in general , therefore , the growth of
wood may bo reduced either by the re
moval of foliage which reduces the
working surface or bjr shading whioh
somewhat checks the activity of the fol
iage by hindering light action.
The flow of sap in trees is not well
understood. In a general way it maybe
said that the sap-
TRANSPIRATION. WOJ(1 ( ( transmits the
water from the roots to the leaves where
a part enters into the assimilated sap
and goes to build up the plant and the
remainder which is by far the greater
part passes off as vapor. The amount
thus transpired varies greatly with the
species , ago of the tree , amount of foli
age at work , amount of light at its dis
posal , climatic conditions and the condi
tion of tree growth. The amount of
water transpired is so large in compari
son to the amount retained in the tree
that while an acre of forest may store in
its trees 1,000 pounds of carbon , 15 or 20
pounds of mineral substances and 5,000
pounds of water in a year it may have
taken from the soil and given off to the
air from 500,000 to 1,500,000 pounds of
water or from one quarter to one-half
as much as agricultural crops. It has
been estimated that the leaves of decid-
ous trees transpire one-sixth to oue-
liird as much water as an equal surface
f water. Large deciduous trees un-
oubtedly give off as much as a barrel
f water a day in dry summer weather.
Coniferous trees transpire much less
vater than most deciduous trees ; fre-
[ uently not over one-sixth as much.
Mineral substances are taken up in
mall quantities and consist mostly of
ime , magnesia and potash. They are
arried to the leaves where they ore used
perhaps also on their passage through
he tree ) with a part of the water in
bed preparation. The main part of the
mineral substances taken up remains as
he water transpires in the leaves and
ouug twigs and is returned to the soil
vheii the leaves are shed , and when the
jree is cut and the brush loft to decom
pose and make humus.
The soil of woodlands is improvet
: rom year to year if the leaves and littei
ire allowed to remain on the ground anc
Ire is kept out , since the mineral matters
taken up by the tree are largely returnee"
: o the soil in a more soluble form anc
; he amount of humus is increased. Foi
; his reason there is no need of alternat
ing woodland crops.
Almost any soil can furnish a sullici
cut quantity of mineral substances foi
he production of a crop of trees pro
vided it is moist and the leaf mould is
not removed. Good soils will continue
to furnish mineral matter in sufficient
quantity even if a portion of the leaf
mould is carried away. If however this
removal is continued annually for a long
period , any but exceedingly fertile soils
are likely to become exhausted just as
laud on which field crops are grown can
not produce crops forever without man-
iiring.
In the spring the tree starts into
growth and feeds on the plant food
stored up the pro-
YKARLY ROUNDS , . , , , imr . , , , „ „ . . . 3
l > UvlJ.IJll J V-til. f
OF TREE LIFE.
1
commence furnishing plant food. These
two sources of food push the growth
along very rapidly in the spring and :
early summer. By the first of July the
food stored up the previous season is ex
hausted in many trees and growth is en
tirely dependent upon the food furnished [
by the leaves. The growth at this time
is generally much slower than in the
spring and as the capacity of the tree
for building up plant food increases it
commences to store up starch , sugar and
other foods in its cells with which to
start growth the following spring and
he cell walls become thicker and firmer.
This maturing of the tree is termed the
'ipcniny of the wood and when completed
: he tree is ready for winter. Our hard
est trees generally ripen their wood
early in the autumn and then cease
growing although probably some food is
jeiug stored up so long as the leaves re
main green on the trees.
"With very few exceptions all plants
require an occasional rest period for
their best develop
REST PERIOD
ment. Some species
OP PLANTS.
cies get it natur
ally by being dried and others by being
frozen. And even when plants are kept
under growing conditions the year round
they have periods of rest and of excite
ment. During the rest period the plants
undergo very few changes and yet there
is undoubtedly some growth during mild
weather in winter and as evaporation
must be going on most of the time from
twigs and buds , water must be supplied
from the roots.
After many careful experiments A. L.
Knisely , M. S. , concludes that a soft
maple standing 80
WATER LOST BY
or 555 feet high
TREES IN WINTER.
with a trunk 15 to
18 inches in diameter near the ground ,
exposing from 750 to 800 square feet of
bark surface , may lose daily by evapora
tion from G to 7 pounds of water when
dormant. An apple tree 80 years old
and 15 inches in diameter at the base ,
exposing from 800 to 1,000 square feet of
bark surface may lose daily while dor
mant from 10 to 18 pounds of water.
These figures are from results obtained
during winter weather in Now York
where the relative humidity of the air is
; iigher than in Minnesota which would
lesson evaporation. It is probable that
during our winters here the evaporation
from trees will greatly exceed that in
Now York and that greater evaporation
is nearly always responsible for some
trees being tender here and hardy in
Now York and other places with similar
conditions.
Wo know that in this section after a
prolonged period of severely cold
weather , the twigs of soft maple , apple
and some other trees have a decidedly
shrivelled appearance which disappears
after a few days of mild weather. Soft
maple trees standing on dry land will
sometime in the spring appear to have
been dried out and to have become
partly or entirely dead. It is probable
that during our coldest weather very lit-
tie , if any , moisture can bo supplied from
the roots which nuiy account for this
shrivelled condition.
Sometimes warm , moist weather in
late autumn will cause trees to start a
strong second
SECOND GROWTH.
jn October
which draws on the stored plant food