William Shakespeare - "Der Erste Theil von Koenig Heinrich dem vierten"

F. Morley Fletcher - "Wood Block Printing"

Andrew Barton Paterson - "An Outback Marriage"

Lewis Madison Terman - "The Measurement of Intelligence"

Annual Bibliography of Commonwealth Literature 2007
This paper argues that discourses of love in Ghanaian market literature for youth offer a view into complex negotiations of agency and empowerment. Drawing on Deborah Durham's notion of youth as "social `shifters'" and Francis Nyamnjoh's conception of the "interconnectedness" of agency, I take Ghanaian market literature as one specific case of how African literature for youth foregrounds questions of continuity and change as African societies enter into increasingly complex global relations. In this literature for youth, received notions of love, often constructed out of impressions from American pop and hip hop music, carry new notions of agency that compete with existing "domesticated" forms. Authors like Ike Tandoh and Evelyn Tay employ discourses of love to offer youth alternative avenues for empowerment in a context of socio-economic disenfranchizement. In a creative process of "straddling", this writing both reveals and reproduces the contradictions that obtain in youth configurations of agency.

Elements of Structural and Systematic Botany

D >> Douglas Houghton Campbell >> Elements of Structural and Systematic Botany





ORDER V.--_Characeae_.

The _Characeae_, or stone-worts, as some of them are called, are so
very different from the other green algae that it is highly probable
that they should be separated from them.

The type of the order is the genus _Chara_ (Fig. 23), called
stone-worts from the coating of carbonate of lime found in most of
them, giving them a harsh, stony texture. Several species are common
growing upon the bottom of ponds and slow streams, and range in size
from a few centimetres to a metre or more in height.

The plant (Fig. 23, _A_) consists of a central jointed axis with
circles of leaves at each joint or node. The distance between the
nodes (internodes) may in the larger species reach a length of several
centimetres. The leaves are slender, cylindrical structures, and like
the stem divided into nodes and internodes, and have at the nodes
delicate leaflets.

At each joint of the leaf, in fruiting specimens, attached to the
inner side, are borne two small, roundish bodies, in the commoner
species of a reddish color (Fig. 23, _A_, _r_). The lower of the two
is globular, and bright scarlet in color; the other, more oval and
duller.

Examined with a lens the main axis presents a striated appearance. The
whole plant is harsh to the touch and brittle, owing to the limy
coating. It is fastened to the ground by fine, colorless hairs, or
rootlets.

[Illustration: FIG. 23.--_A_, plant of a stone-wort (_Chara_),
one-half natural size. _r_, reproductive organs. _B_, longitudinal
section through the apex. _S_, apical cell. _x_, nodes. _y_,
internodes. _C_, a young leaf. _D_, cross section of an internode.
_E_, of a node of a somewhat older leaf. _F_, _G_, young sexual organs
seen in optical section. _o_, ooegonium. _An._ antheridium. _H_,
superficial view. _G_, _I_, group of filaments containing
spermatozoids. _J_, a small portion of one of these more magnified,
showing a spermatozoid in each cell. _K_, free spermatozoids. _L_, a
piece of a leaf with ripe ooegonium (_o_), and antheridium (_An._).
_B_, _H_, x 150. _J_, _K_, x 300. _I_, x 50. _L_, x 25.]

By making a series of longitudinal sections with a sharp razor
through the top of the plant, and magnifying sufficiently, it is
found to end in a single, nearly hemispherical cell (Fig. 23, _B_,
_S_). This from its position is called the "apical cell," and from
it are derived all the tissues of the plant. Segments are cut off
from its base, and these divide again into two by a wall parallel to
the first. Of the two cells thus formed one undergoes no further
division and forms the central cell of an internode (_y_); the other
divides repeatedly, forming a node or joint (_x_).

As the arrangement of these cells is essentially the same in the
leaves and stem, we will examine it in the former, as by cutting
several cross-sections of the whole bunch of young leaves near the
top of the plant, we shall pretty certainly get some sections
through a joint. The arrangement is shown in Figure 23, _E_.

As the stem grows, a covering is formed over the large internodal
cell (_y_) by the growth of cells from the nodes. These grow both
from above and below, meeting in the middle of the internode and
completely hiding the long axial cell. A section across the
internode shows the large axial cell (_y_) surrounded by the
regularly arranged cells of the covering or cortex (Fig. 23, _D_).

All the cells contain a layer of protoplasm next the wall with
numerous oval chloroplasts. If the cells are uninjured, they often
show a very marked movement of the protoplasm. These movements are
best seen, however, in forms like _Nitella_, where the long
internodal cells are not covered with a cortex. In _Chara_ they are
most evident in the root hairs that fasten the plant to the ground.

The growth of the leaves is almost identical with that of the stem,
but the apical growth is limited, and the apical cell becomes
finally very long and pointed (Fig. 23, _C_). In some species the
chloroplasts are reddish in the young cells, assuming their green
color as the cells approach maturity.

The plant multiplies non-sexually by means of special branches that
may become detached, but there are no non-sexual spores formed.

The sexual organs have already been noticed arising in pairs at the
joints of the leaves. The ooegonium is formed above, the antheridium
below.

The young ooegonium (_F_, _O_) consists of a central cell, below
which is a smaller one surrounded by a circle of five others, which
do not at first project above the central cell, but later completely
envelop it (_G_). Each of these five cells early becomes divided
into an upper and a lower one, the latter becoming twisted as it
elongates, and the central cell later has a small cell cut off from
its base by an oblique wall. The central cell forms the egg cell,
which in the ripe ooegonium (_L_, _O_) is surrounded by five,
spirally twisted cells, and crowned by a circle of five smaller
ones, which become of a yellowish color when full grown. They
separate at the time of fertilization to allow the spermatozoids to
enter the ooegonium.

The antheridium consists at first of a basal cell and a terminal
one. The latter, which is nearly globular, divides into eight nearly
similar cells by walls passing through the centre. In each of these
eight cells two walls are next formed parallel to the outer surface,
so that the antheridium (apart from the basal cell) contains
twenty-four cells arranged in three concentric series (_G_, _an._).
These cells, especially the outer ones, develop a great amount of a
red pigment, giving the antheridium its characteristic color.

The diameter of the antheridium now increases rapidly, and the
central cells separate, leaving a large space within. Of the inner
cells, the second series, while not increasing in diameter,
elongate, assuming an oblong form, and from the innermost are
developed long filaments (_I_, _J_) composed of a single row of
cells, in each of which is formed a spermatozoid.

The eight outer cells are nearly triangular in outline, fitting
together by deeply indented margins, and having the oblong cells
with the attached filaments upon their inner faces.

If a ripe antheridium is crushed in a drop of water, after lying a
few minutes the spermatozoids will escape through small openings in
the side of the cells. They are much larger than any we have met
with. Each is a colorless, spiral thread with about three coils, one
end being somewhat dilated with a few granules; the other more
pointed, and bearing two extremely long and delicate cilia (_K_). To
see the cilia it is necessary to kill the spermatozoids with iodine
or some other reagent.

After fertilization the outer cells of the ooegonium become very
hard, and the whole falls off, germinating after a sufficient period
of rest.

According to the accounts of Pringsheim and others, the young plant
consists at first of a row of elongated cells, upon which a bud is
formed that develops into the perfect plant.

There are two families of the _Characeae_, the _Chareae_, of which
_Chara_ is the type, and the _Nitelleae_, represented by various
species of _Nitella_ and _Tolypella_. The second family have the
internodes without any cortex--that is, consisting of a single long
cell; and the crown at the top of the ooegonium is composed of ten
cells instead of five. They are also destitute of the limy coating of
the _Chareae_.

Both as regards the structure of the plant itself, as well as the
reproductive organs, especially the very complex antheridium, the
_Characeae_ are very widely separated from any other group of plants,
either above or below them.




CHAPTER VI.

THE BROWN ALGAE (_Phaeophyceae_).


[Illustration: FIG. 24.--Forms of diatoms. _A_, _Pinnularia_. i, seen
from above; ii, from the side. _B_, _Fragillaria_ (?). _C_,
_Navicula_. _D_, _F_, _Eunotia_. _E_, _Gomphonema_. _G_, _Cocconeis_.
_H_, _Diatoma_. All x 300.]

These plants are all characterized by the presence of a brown pigment,
in addition to the chlorophyll, which almost entirely conceals the
latter, giving the plants a brownish color, ranging from a light
yellowish brown to nearly black. One order of plants that possibly
belongs here (_Diatomaceae_) are single celled, but the others are for
the most part large seaweeds. The diatoms, which are placed in this
class simply on account of the color, are probably not closely related
to the other brown algae, but just where they should be placed is
difficult to say. In some respects they approach quite closely the
desmids, and are not infrequently regarded as related to them. They
are among the commonest of organisms occurring everywhere in stagnant
and running water, both fresh and salt, forming usually, slimy,
yellowish coatings on stones, mud, aquatic plants, etc. Like the
desmids they may be single or united into filaments, and not
infrequently are attached by means of a delicate gelatinous stalk
(Fig. 25).

[Illustration: FIG. 25.--Diatoms attached by a gelatinous stalk.
x 150]

They are at once distinguished from the desmids by their color,
which is always some shade of yellowish or reddish brown. The
commonest forms, _e.g._ _Navicula_ (Fig. 24, _C_), are boat-shaped
when seen from above, but there is great variety in this respect.
The cell wall is always impregnated with large amounts of flint, so
that after the cell dies its shape is perfectly preserved, the flint
making a perfect cast of it, looking like glass. These flinty shells
exhibit wonderfully beautiful and delicate markings which are
sometimes so fine as to test the best lenses to make them out.

This shell is composed of two parts, one shutting over the other
like a pill box and its cover. This arrangement is best seen in such
large forms as _Pinnularia_ (Fig. 24, _A_ ii).

Most of the diatoms show movements, swimming slowly or gliding over
solid substances; but like the movements of _Oscillaria_ and the
desmids, the movements are not satisfactorily understood, although
several explanations have been offered.

They resemble somewhat the desmids in their reproduction.


THE TRUE BROWN ALGAE.

These are all marine forms, many of great size, reaching a length in
some cases of a hundred metres or more, and showing a good deal of
differentiation in their tissues and organs.

[Illustration: FIG. 26.--_A_, a branch of common rock weed (_Fucus_),
one-half natural size. _x_, end of a branch bearing conceptacles. _B_,
section through a conceptacle containing ooegonia (_og._), x 25. _C_,
_E_, successive stages in the development of the ooegonium, x 150. _F_,
_G_, antheridia. In _G_, one of the antheridia has discharged the mass
of spermatozoids (_an._), x 150.]

One of the commonest forms is the ordinary rock weed (_Fucus_), which
covers the rocks of our northeastern coast with a heavy drapery for
several feet above low-water mark, so that the plants are completely
exposed as the tide recedes. The commonest species, _F. vesiculosus_
(Fig. 26, _A_), is distinguished by the air sacs with which the stems
are provided. The plant is attached to the rock by means of a sort of
disc or root from which springs a stem of tough, leathery texture, and
forking regularly at intervals, so that the ultimate branches are very
numerous, and the plant may reach a length of a metre or more. The
branches are flattened and leaf-like, the centre traversed by a
thickened midrib. The end of the growing branches is occupied by a
transversely elongated pit or depression. The growing point is at the
bottom of this pit, and by a regular forking of the growing point the
symmetrical branching of the plant is brought about. Scattered over
the surface are little circular pits through whose openings protrude
bunches of fine hairs. When wet the plant is flexible and leathery,
but it may become quite dry and hard without suffering, as may be seen
when the plants are exposed to the sun at low tide.

The air bladders are placed in pairs, for the most part, and buoy up
the plant, bringing it up to the surface when covered with water.

The interior of the plant is very soft and gelatinous, while the outer
part forms a sort of tough rind of much firmer consistence. The ends
of some of the branches (Fig. 26, _A_, _x_) are usually much swollen,
and the surface covered with little elevations from which may often be
seen protruding clusters of hairs like those arising from the other
parts of the plant. A section through one of these enlarged ends shows
that each elevation corresponds to a cavity situated below it. On some
of the plants these cavities are filled with an orange-yellow mass; in
others there are a number of roundish olive-brown bodies large enough
to be easily seen. The yellow masses are masses of antheridia; the
round bodies, the ooegonia.

If the plants are gathered while wet, and packed so as to prevent
evaporation of the water, they will keep perfectly for several days,
and may readily be shipped for long distances. If they are to be
studied away from the seashore, sections for microscopic examination
should be mounted in salt water (about 3 parts in weight of common
salt to 100 of water). If fresh material is not to be had, dried
specimens or alcoholic material will answer pretty well.

To study the minute structure of the plant, make a thin
cross-section, and mount in salt water. The inner part or pith is
composed of loosely arranged, elongated cells, placed end to end,
and forming an irregular network, the large spaces between filled
with the mucilaginous substance derived from the altered outer walls
of these cells. This mucilage is hard when dry, but swells up
enormously in water, especially fresh water. The cells grow smaller
and more compact toward the outside of the section, until there are
no spaces of any size between those of the outside or rind. The
cells contain small chloroplasts like those of the higher plants,
but owing to the presence of the brown pigment found in all of the
class, in addition to the chlorophyll, they appear golden brown
instead of green.

No non-sexual reproductive bodies are known in the rock weeds,
beyond small branches that occur in clusters on the margins of the
main branches, and probably become detached, forming new plants. In
some of the lower forms, however, _e.g._ _Ectocarpus_ and
_Laminaria_ (Fig. 28, _A_, _C_), zooespores are formed.

The sexual organs of the rock weed, as we have already seen, are
borne in special cavities (conceptacles) in the enlarged ends of
some of the branches. In the species here figured, _F. vesiculosus_,
the antheridia and ooegonia are borne on separate plants; but in
others, _e.g._ _F. platycarpus_, they are both in the same
conceptacle.

The walls of the conceptacle (Fig. 26, _B_) are composed of closely
interwoven filaments, from which grow inward numerous hairs, filling
up the space within, and often extending out through the opening at
the top.

The reproductive bodies arise from the base of these hairs. The
ooegonia (Fig. 26, _C_, _E_) arise as nearly colorless cells, that
early become divided into two cells, a short basal cell or stalk and
a larger terminal one, the ooegonium proper. The latter enlarges
rapidly, and its contents divide into eight parts. The division is
at first indicated by a division of the central portion, which
includes the nucleus, and is colored brown, into two, four, and
finally eight parts, after which walls are formed between these. The
brown color spreads until the whole ooegonium is of a nearly uniform
olive-brown tint.

When ripe, the upper part of the ooegonium dissolves, allowing the
eight cells, still enclosed in a delicate membrane, to escape
(Fig. 27, _H_). Finally, the walls separating the inner cells of the
ooegonium become also absorbed, as well as the surrounding membrane,
and the eight egg cells escape into the water (Fig. 27, _I_) as
naked balls of protoplasm, in which a central nucleus may be dimly
seen.

The antheridia (Fig. 26, _F_, _G_) are small oblong cells, at first
colorless, but when ripe containing numerous glistening, reddish
brown dots, each of which is part of a spermatozoid. When ripe, the
contents of the antheridium are forced out into the water (_G_),
leaving the empty outer wall behind, but still surrounded by a thin
membrane. After a few minutes this membrane is dissolved, and the
spermatozoids are set free. These (Fig. 27, _K_) are oval in form,
with two long cilia attached to the side where the brown speck, seen
while still within the antheridium, is conspicuous.

The act of fertilization may be easily observed by laying fresh
antheridia into a drop of water containing recently discharged egg
cells. To obtain these, all that is necessary is to allow freshly
gathered plants to remain in the air until they are somewhat dry,
when the ripe sexual cells will be discharged from the openings of
the conceptacles, exuding as little drops, those with antheridia
being orange-yellow; the masses of ooegonia, olive. Within a few
minutes after putting the ooegonia into water, the egg cells may be
seen to escape into the water, when some of the antheridia may be
added. The spermatozoids will be quickly discharged, and collect
immediately in great numbers about the egg cells, to which they
apply themselves closely, often setting them in rotation by the
movements of their cilia, and presenting a most extraordinary
spectacle (_J_). Owing to the small size of the spermatozoids, and
the opacity of the eggs, it is impossible to see whether more than
one spermatozoid penetrates it; but from what is known in other
cases it is not likely. The egg now secretes a wall about itself,
and within a short time begins to grow. It becomes pear-shaped, the
narrow portion becoming attached to the parent plant or to some
other object by means of rootlets, and the upper part grows into the
body of the young plant (Fig. 27, _M_).

[Illustration: FIG. 27.--_H_, the eight egg cells still surrounded by
the inner membrane of the ooegonium. _I_, the egg cells escaping into
the water. _J_, a single egg cell surrounded by spermatozoids. _K_,
mass of spermatozoids surrounded by the inner membrane of the
antheridium. _L_, spermatozoids. _M_, young plant. _r_, the roots.
_K_, x 300; _L_, x 600; the others, x 150.]

The simpler brown seaweeds, so far as known, multiply only by means of
zooespores, which may grow directly into new plants, or, as has been
observed in some species, two zooespores will first unite. A few, like
_Ectocarpus_ (Fig. 28, _A_), are simple, branched filaments, but most
are large plants with complex tissues. Of the latter, a familiar
example is the common kelp, "devil's apron" (_Laminaria_), often three
to four metres in length, with a stout stalk, provided with root-like
organs, by which it is firmly fastened. Above, it expands into a
broad, leaf-like frond, which in some species is divided into strips.
Related to the kelps is the giant kelp of the Pacific (_Macrocystis_),
which is said sometimes to reach a length of three hundred metres.

[Illustration: FIG. 28.--Forms of brown seaweeds. _A_, _Ectocarpus_,
x 50. Sporangia (_sp._). _B_, a single sporangium, x 150. _C_, kelp
(_Laminaria_), x 1/8. _D_, _E_, gulf weed (_Sargassum_). _D_, one-half
natural size. _E_, natural size. _v_, air bladders. _x_, conceptacle
bearing branches.]

The highest of the class are the gulf weeds (_Sargassum_), plants of
the warmer seas, but one species of which is found from Cape Cod
southward (Fig. 28, _D_, _E_). These plants possess distinct stems and
leaves, and there are stalked air bladders, looking like berries,
giving the plant a striking resemblance to the higher land plants.




CHAPTER VII.

CLASS III.--THE RED ALGAE (_Rhodophyceae_).


These are among the most beautiful and interesting members of the
plant kingdom, both on account of their beautiful colors and the
exquisitely graceful forms exhibited by many of them. Unfortunately
for inland students they are, with few exceptions, confined to salt
water, and consequently fresh material is not available. Nevertheless,
enough can be done with dried material to get a good idea of their
general appearance, and the fruiting plants can be readily preserved
in strong alcohol. Specimens, simply dried, may be kept for an
indefinite period, and on being placed in water will assume perfectly
the appearance of the living plants. Prolonged exposure, however, to
the action of fresh water extracts the red pigment that gives them
their characteristic color. This pigment is found in the chlorophyll
bodies, and usually quite conceals the chlorophyll, which, however,
becomes evident so soon as the red pigment is removed.

The red seaweeds differ much in the complexity of the plant body, but
all agree in the presence of the red pigment, and, at least in the
main, in their reproduction. The simpler ones consist of rows of
cells, usually branching like _Cladophora_; others form cell plates
comparable to _Ulva_ (Fig. 30, _C_, _D_); while others, among which is
the well-known Irish moss (_Chondrus_), form plants of considerable
size, with pretty well differentiated tissues. In such forms the outer
cells are smaller and firmer, constituting a sort of rind; while the
inner portions are made up of larger and looser cells, and may be
called the pith. Between these extremes are all intermediate forms.

They usually grow attached to rocks, shells, wood, or other plants,
such as the kelps and even the larger red seaweeds. They are most
abundant in the warmer seas, but still a considerable number may be
found in all parts of the ocean, even extending into the Arctic
regions.

[Illustration: FIG. 29.--_A_, a red seaweed (_Callithamnion_), of the
natural size. _B_, a piece of the same, x 50. _t_, tetraspores. _C_
i-v, successive stages in the development of the tetraspores, x 150.
_D_ I, II young procarps. _tr._ trichogyne. iii, young; iv, ripe spore
fruit. I, III, x 150. iv, x 50. _E_, an antheridium, x 150. _F_, spore
fruit of _Polysiphonia_. The spores are here surrounded by a case,
x 50.]

The methods of reproduction may be best illustrated by a specific
example, and preferably one of the simpler ones, as these are most
readily studied microscopically.

The form here illustrated (_Callithamnion_) grows attached to wharves,
etc., below low-water mark, and is extremely delicate, collapsing
completely when removed from the water. The color is a bright rosy
red, and with its graceful form and extreme delicacy it makes one of
the most beautiful of the group.

If alcoholic material is used, it may be mounted for examination
either in water or very dilute glycerine.

The plant is composed of much-branched, slender filaments, closely
resembling _Cladophora_ in structure, but with smaller cells
(Fig. 29, _B_). The non-sexual reproduction is by means of special
spores, which from being formed in groups of four, are known as
tetraspores. In the species under consideration the mother cell of
the tetraspores arises as a small bud near the upper end of one of
the ordinary cells (Fig. 29, _C_ i). This bud rapidly increases in
size, assuming an oval form, and becoming cut off from the cell of
the stem (Fig. 29, _C_ ii). The contents now divide into four equal
parts, arranged like the quadrants of a sphere. When ripe, the wall
of the mother cell gives way, and the four spores escape into the
water and give rise to new plants. These spores, it will be noticed,
differ in one important particular from corresponding spores in most
algae, in being unprovided with cilia, and incapable of spontaneous
movement.

Occasionally in the same plant that bears tetraspores, but more
commonly in special ones, there are produced the sexual organs, and
subsequently the sporocarps, or fruits, developed from them. The
plants that bear them are usually stouter that the non-sexual ones,
and the masses of ripe carpospores are large enough to be readily
seen with the naked eye.

If a plant bearing ripe spores is selected, the young stages of the
female organ (procarp) may generally be found by examining the
younger parts of the plant. The procarp arises from a single cell of
the filament. This cell undergoes division by a series of
longitudinal walls into a central cell and about four peripheral
ones (Fig. 29, _D_ i). One of the latter divides next into an upper
and a lower cell, the former growing out into a long, colorless
appendage known as a trichogyne (Fig. 29, _D_, _tr._).

The antheridia (Fig. 29, _E_) are hemispherical masses of closely
set colorless cells, each of which develops a single spermatozoid
which, like the tetraspores, is destitute of cilia, and is dependent
upon the movement of the water to convey it to the neighborhood of
the procarp. Occasionally one of these spermatozoids may be found
attached to the trichogyne, and in this way fertilization is
effected. Curiously enough, neither the cell which is immediately
fertilized, nor the one beneath it, undergo any further change; but
two of the other peripheral cells on opposite sides of the filament
grow rapidly and develop into large, irregular masses of spores
(Fig. 29, _D_ III, IV).

Copyright (c) 2007. topboookz.com. All rights reserved.