Vermont farmer. [volume] (Newport, Orleans County, Vt.) 1870-1877, 1875-02-26
Principles of Horticulture.
III. STEM.

III. STEM.
81. The stem is that part of the plant
which is developed above ground, and which
took an upward direction at the period of
termination.
So. 1t consists of a woody axis, covered
by bark having stomata on its surface, bear
ing leaves with leaf.buds in their axille, and
producing flowers and fruit.
SO. The points where leaves are born are
called NOdi the spaces between the leaves
are Internodi.
80. The more erect stem grows, the
more vigorous it is and the more it devi.
ates from this direction TO a horizontal or
pendulous position, the less is it vigorous
81. Some stems are developed under
ground, such as the Tubers of the Potato
and the Cormus Of the Crocus but they are
known from roots by the presence of leaves,
and regular leaf.buds, upon their surface.
60. Stems increase in diameter in two
ways.
63. Either by the addition of new matter
to the outside of the wood and the inside of
bark; when they are EroyenouS; ex. Oak.
81. Or by the addition of new matter to
their inside; when they are EndogenouS =;
ex. Cane.
60. In Exogenous stems, the central por-
ton, which is harder and darker than at the
circumference, is called Heart Wood while
the exterior, which is softer and lighter is
called AlJurnum or Sap Wood
&c. The inside of the bark of such stems
has also the technical name of Liber.
81. The heart wood was, when young, AL
burnum, and afterwards changed its nature
by becoming the receptacle of certain secre.
tionS peculiar to the species
6S. Hence the greater durability of heart
wood than of sap wood. While the latter
is newly formed empty tissue, almost as per-
ishable as bark itself, the former is protect
ed against destruction by the introduction Of
secretions that become solid matter, which is
often insoluble in water, and never permeabe
in air.
90. The secretions by which heart
wood is solidfed are prepared in the leaves,
whence they are sent downwards through the
bark, and from the bark communicated to tho
central part Of the stem.
70. The channels through which this COM
muuicaton take place are called Medullary
Rays or Sacer Gram.
II. Medulary rays are plates of cellular
tissue, in very compressed state, passing
from the pith into the bark.
70. The wood itself is composed of tubes
consisting of woody fiber and vascular tissue,
imbedded lOngtudinally in cellular sub
stance.
73. This cellular substance only develops
horizontally; and it is to it that the peculiar
character of different kinds of wood is chiefly
due.
"a For this reason the wood of the stock
OF grated plant will never become ike
that of its scion, although, as it will be here
after seen, the woody matter of the stock
must all originate in the scion.
75. The stem of an exonenous plant NAV
therefore bo compared to a piece of linen,
Of which tho weft is composed of cellular
tissue, and the warp Of fbrous and vascular
tissue.
70. In the spring and autumn a viscid
substance is secreted between the wood and
the liber, called the Cam5ium.
II. This cambium appears to be the mat
ter out OF which the cellular horizontal sub
stance of the stem is organized.
78, In Indigenous stems the portion at
the circumference is harder than at the GEN.
tire; and there is no separable bark.
70. Their stems consist of bundles Of
woody matter, imbedded in cellular tissue
surrounded by woody fibre.
80. The stem is not only the peculiar Sc.
cretions of species but is also the medium
through which the sap flows in its passage
from the roots INTO the leaves.
81. In exogenous stems it certainly rises
through the aburnum, and descends through
the bark.
50. Ia endogeuous stems it probably rises
through the bundles of wood, and descends
through the cellular substance; but this is
uncertain.
S3. Stems have the power Of propagating
an individual only by means of their LEAF.
BUDs. II destitute Of leai-buds, they have
no power Of multiplication, except fOrtuitous.
ly.