Sacramento daily record-union. [volume] (Sacramento [Calif.]) 1875-1891, 1882-04-01

to the fact that new cells and fbers are
constantly being formed in the interior of
the stem, and hence the nane-inside
growers. In some species of the endo-
gems the shell-like coat becomes in
time so hardened that the transverse growth
of the plant practically ceases, and
it can only increase in hight. By the con-
slant increase of fibers in the interior of
such plants, and from their inability to all
find egress IL the growing extremities, the
life of the plant is sometimes literally
choked out of it. In some indigenous
plants the stems are hollow except at the
notes.-the grasses-and in others there are
no visible nodes, but there is pith of
cellular tissue running the entire length of
the stem. This form of structure may be
seen in our common water-rushes. The
seed of the endogens generally consists of
but one single part, and has only one CO.
tyledon hence the name mono cotyledon-
GUS On the other hand,
THE SEED OF THE EXoGENs
Generally consists of two loosely united
parts or cotyledons they have therefore
been termed the dicotyledonous plants
exogenous plants. The growth of exo-
genous plants is carried on by the contina.
Gus deposition of layers of newly-formed
matter near the outside of the stem. This
growth takes place just under the cpl.
dermis or skin. The growth of cells, duets
and fibers originates in the cell tissues ad-
jacent to the epidermis. The products of this
growth are generally disposed in circle
which, as the growth progresses, closes up
into ring or zone, forming continuous
layer OF wood, which surrounds the pith,
and is itself inclosed by the bark of the
tree. The growth proceeds by the
formation of new circles, rings and
zones of fiber, and which ars de-
posted between the old wood and
the epidermis. By this manner of growth
the new material is always placed outside
of the old layers of wood. The wood of
exogens is dense or soft, accordingly as the
wood and vascular, or as the cellular tissue
predominates. In trees of hard and dense
wood the growth is almost always slow
and takes place by the deposition of thin
coats of dense, hard and thickened wood
cells. The stem of most exogenous plants
contains pith. This pith consists of cellu.
lar tissue, which in young plants is filled
with sap, but the pith of old plants most
generally contains no liquid and seems to
perform no functions at all. In plants of
rapid growth the pith is often broken and
almost obliterated, leaving cylindrical
aperture running the entire length of the
stem. The bark or rind in the early stages
of plant growth consists simply of thin
skin. The bark of mature and older plants
consists of three distinct parts, the hber,
the outer bark, and
THE EPIDERMIS.
The hber or inner bark, or bast tissue,
as it is sometimes called, is made up Of
thick, elongated fibers, remarkable for
their length and fexibility. They cohere
together in bundles or bands, and 1t is that
which imparts the strength to the inner
bark of most stems. 1t is the bast tissue
of the hemp, flax and other plants of tex
tile fiber hich makes them valuable for the
manufacture of fabrics. The outer bark
consists of two distinct layers, the green
or cellular envelope, and the corky layer.
The first is made up of loose, cellular
tissue with thin and tender cell walls.
The cells contain liquids, and chlorophyl,
| which gives the visible green color to young
barks. By pairing off the corky layer from
| the bark Of any living tree, there will be
found green-colored sappy layer beneath.
| This is the cellular envelope or green layer.
The corky layer is the most conspicuous
part of most barks. 1t gives to all stems
and branches their characteristic hue.
In some trees this layer is almost abnor-
mally developed, giving rise to thick layers
Of material, which is collected and which
forms the commercial cork. The corky
layer of some trees is deeply and irregu-
larly cleft, and in others it separates in
| folds or sheets, often of considerable size.