While the actions which lead to the various effects on the external
appearance of a tree, described in the former paper, are going on,
many important changes occur in the internal parts, producing
alterations not less admirable, whether in respect of the tree itself,
or of the ends to which it may be rendered subservient. The base of an
exogenous tree is not merely widened by the superposition of annual
layers of wood over the first shoot, by which it gains greater
mechanical power to support the extending head of wide-spreading
branches, but the central portion is, in most cases, progressively
rendered more and more solid by the deposition in it of various
secretions prepared by the leaves, and transmitted from them through
the medullary rays into this part as their ultimate resting-place.
The fibres descending from the developing buds on the stem, and
passing between the plates of cellular tissue, which constitute the
medullary rays, and the cells of which have a horizontal direction,
are but the basis of the vegetable fabric. The stem of an exogenous
plant has been compared to a piece of linen, of which the weft is
composed of cellular tissue, and the warp of fibrous and vascular
tissue--crossing each other. Now, after the portion is once formed,
which is woven every year by the wondrous machinery set to work for
this purpose, it receives no fresh texture, yet each fibre remains a
conducting tube to transmit the sap upwards, or, in the course of
time, becomes charged with various principles, prepared, as already
stated, by the leaves, and returned to the central part by that
apparatus or system of canals for their transit inwards, the medullary
rays, and at last are obstructed, so that no passage of fluid is
effected through the inner layers of wood. But for every layer that is
thus blocked up, a new one, which will continue pervious, is formed
exterior to those already existing, so that a constant provision is
made for carrying on the vital processes; to accomplish which, a free
channel from the points of the roots to the surface of the leaves is
absolutely necessary. The outer strata, produced by a tree of
considerable age, are observed to be thinner than those formed at an
earlier period, and become successively thinner and thinner, so that
ultimately, if accident should not have previously caused it, the
death of the tree is inevitable. The portions which are obstructed
constitute the _duramen_ or heartwood, the pervious portion the
_alburnum_ or sapwood. The original tissue is colourless; but
according to the nature of the secretions deposited in it, the
heartwood is either of a deeper colour, sometimes party-coloured, or
at least of a much greater specific gravity than the sapwood. The
removal of the juices by any solvent restores the wood to its
primitive hue, and renders it again light. The difference of weight of
a cubic foot of wood depends not merely on the different quantity of
vegetable tissue compressed into a given space, in the first
construction of the tree, but also on the quantity and quality of the
secretions ultimately lodged in it. The same species of tree will
present a difference in this respect, according to the country or
situation where it grew, and also according to the character of the
seasons during the time it flourished. According to the nature of the
tree, if placed in favourable circumstances in reference to soil and
weather, it invariably prepares and lodges in the stem those
principles which it was designed to elaborate--the oak preparing
tannin--the sugar-maple preparing its saccharine juice. That the
primary object of these was some advantage to the tree itself can
scarcely be doubted, but the secondary applications of which they are
capable, give reason to suppose that these also were contemplated in
their formation. The consideration of the means by which they are
formed, and the direct consequences of their formation on the air, by
abstracting certain elements from it, and supplying others, belong to
the subject of leaves; it is the object of the present paper to view
them as formed, and to show their amazing utility.
The mechanical properties of the stems of trees, both exogenous and
endogenous, render them extremely serviceable to mankind. The uses to
which a single species of plant may be put are numerous and important,
of which the reed (arundo phragmites) is an example, for after the
root has assisted in binding and consolidating the soil, the stem is
susceptible of the most varied applications[A].
In a low state of civilization the palm, or a palm-like grass,
supplies all that man requires; of the former of which, the _Mauritia
flexuosa_, or sago-palm of the Oronooko, and still more the _cocos
nucifera_, or cocoa-nut palm; and of the latter, the bamboo (_bambusa
arundinacea_, and other species) are proofs. The bamboo suffices for
all the needs of the humbler Chinese; even their paper, as well as
their abodes, are made of it; and from the materials furnished by the
cocoa-nut tree, not merely food, as shall be afterwards noticed, but
larger and more elegant houses, with all their appurtenances, are
constructed at Goa and other places. The obligations of the Guaraons
to the _Mauritia flexuosa_ cannot be expressed[B]. In proportion as
man rises in civilization, the importance of timber becomes greater,
being a material for which no adequate substitute can be found. It
combines lightness with strength, elasticity with firmness, and
possesses in many instances a durability rivalling, or even
surpassing, that of the rocks yielded to us by the solid substance of
the globe. The adaptation of timber to the numerous wants of civil
life is too familiar to require exposition; but in addition to all the
ends it serves in these points, we have an interesting view presented
to us in considering what a vast quantity of timber is required for
the construction of our shipping, from the countless boats and small
craft employed in our coasting trade up to the larger ships, which are
so many floating towns or communities. These conduce to the
accomplishment of objects of the most momentous nature. Were it not
for our shipping we should still be in the condition described by the
Romans, as Britons cut off from the rest of the world.--But by their
means we now visit without restraint,
"Earth's farthest verge, and ocean's wildest shore,"[C]
and though, in times past, they have been too often used as engines
fraught with destruction, directed by man against his fellow man, let
us hope that they may be required in future only to convey in amicable
interchange the produce of one country to another, or to bear to his
destination the missionary bent on extending the blessings of that
religion whose spirit is "peace on earth, good will among the children
of men[D]."
As a means of supplying fuel, without which man must remain constantly
in the savage state, wood is of inestimable value. In the process of
combustion, the elements of the trees enter into new combinations,
evolving both light and heat, which at once maintain life and render
it a state of enjoyment and usefulness. For this purpose in Britain,
we chiefly employ fossil fuel, stored up in the secret places of the
earth, and, therefore, we attach less importance to recent wood; but
other parts of the world are not so favourably situated, and to the
inhabitants of these places fresh, or but lately felled, wood is
necessary for their existence. Even in France, though partially
possessed of coal, it is estimated that the quantity of wood employed
to supply heat, whether for comfort, cooking, or in manufactures which
require a high temperature, amounts to seven-tenths of the entire
consumption. The superiority of wood fuel, whether fossil or recent,
over every other material resorted to with a like intention, shall be
shown in a subsequent part of this paper. I therefore pass on at
present to demonstrate the utility of vegetable substances in
affording the means of subsistence to man and animals.
In the observations I am about to make, it is impossible to avoid
anticipating some of the remarks which belong to the subject of fruits
and seeds as articles of food, since the same principles of nutriment
are found in the stems of certain plants as are deposited in the
fruits or seeds of others.
Though man is omnivorous, and can subsist either on animal or
vegetable food--an arrangement which fits him to dwell in any part of
the habitable globe,--yet he is subject, with regard to the actual
material of his diet, in a remarkable manner, to the influence of
climate, since a particular kind of aliment, which is very appropriate
in one country is improper in another; thus, as we advance from the
equator towards the poles, the necessity for animal food becomes
greater, till, in the very north, it is the sole article of
subsistence. Animal food, from containing nitrogen, is more
stimulating, and, therefore, less suitable for hot climates, where, on
the contrary, saccharine, mucilaginous, and starchy materials are
preferred; hence, in the zone of the tropics, we find produced in
abundance rice, maize, millet, sago, salep, arrowroot, potatoes, the
bread-fruit, banana, and other watery, or mucilaginous fruits.
Quitting this zone, we enter that which produces wheat, and here,
where the temperature is lower, providence has united with the starch
of this grain a peculiar principle (gluten), possessing all the
properties of animal matter, and yielding nitrogen and ammonia in its
decomposition[E]. Thus, by a gradual and almost insensible transition,
nature furnishes to man the food which is most appropriate for him in
each region. In the subtropical zone vegetable diet is still
preferred, but, in chemical constitution, the favourite articles
approximate animal substances. This holds also in the temperate zone,
not only in respect of wheat, but also in the chesnut, which is almost
the sole means of subsistence in some of the mountainous regions of
France, Italy, and Spain, though, instead of the gluten of wheat, this
seed contains albumen, the relation of which to animal food is even
closer than that of gluten. In reviewing the geographical distribution
of the cereal grains[F], we find that starch nearly pure is produced
in the greatest abundance in the hottest parts of the world,
particularly in rice and maize; it becomes associated in the
subtropical regions with an equivalent for animal food; and in still
colder regions, where wheat fails, oats and barley take its place.
These, though possessed of less gluten than wheat, are, nevertheless,
more heating, and, therefore, better calculated for northern
latitudes. The inhabitants of Scotland and Lapland, with their oaten
and barley or rye bread, are thus as thoroughly provided with the best
food, as the Hindoo with his rice or Indian corn[G].
It would be impossible to enumerate the plants which furnish starch in
large proportion, but a few may be given as illustrative of the above
positions. The chemical analysis of those proximate principles of
plants which are mere combinations of water with carbon
(hydro-carbonates or hydrates of carbon) has been already given, but
must here be repeated:--
100 parts consist of
| Water. | Carbon.
Gum (pure gum-arabic) | 58.6 | 41.4
Sugar (pure crystallized) | 57.15 | 42.85
Starch | 56.00 | 44.00
Lignin | 50.00 | 50.00
These are so many mutually convertible products, of which gum may be
looked upon as the basis; indeed gum is that organizable product which
exists most universally in the proper juices of plants. "There are
some instances in which sugar appears to be the first organic compound
formed by the combination of the external elements, as when abundantly
existing in the ascending sap of trees--the maple, for example. Starch
may be considered as little else than gum divided into minute
portions, each of which is enclosed in a membraneous cell (and
containing some incidental particles, which, when starch is burnt,
leave about .23 per cent. of residuum, consisting entirely of
phosphates); and, in this state, it appears to answer very important
ends in the vegetable economy. It is remarked by Decandolle, that,
'while gum itself may be considered the nutrient principle of
vegetation, diffused freely through the structure of the plant, and
constantly in action, starch is apparently the same substance, stored
up in such a manner as not to be readily soluble in the circulating
fluids,' thus forming a reservoir of nutritious matter, which is to be
consumed, like the fat of animals (which it closely resembles in
structure), in supporting the plant at particular periods[H]."
This view explains the fact of starch being found accumulated in
amazing quantity in some plants, more particularly at certain periods
of their existence, as in the cases I am now to cite. The fertility of
some palm-trees is very great, and to furnish nutriment to the
flowers, fruit, and seeds, an enormous supply of starch is needed;
accordingly, in these we find the stem a complete storehouse of this
essential principle. Thus the several palms and palm-like plants,
which yield sago, such as the _sagus Rumphii_, _cycas circinalis_, _C.
revoluta_, _corypha umbraculifera_, _caryota urens_, and _phoenix
farinifera_--trees which are mostly confined within the tropics, at
the moment when the spadices or sheaths containing the bunches of
flowers are visible but not unfolded, furnish an immense portion of
the food of the natives. The _sagus Rumphii_, which abounds in the
islands of the Indian Archipelago, and though one of the humblest of
the palm tribe, seldom exceeding thirty feet in height, is yet, except
the gomuto, the thickest and largest, alone yields a quantity of
nutritious matter far exceeding that of all other cultivated plants,
inasmuch as a tree in its fifteenth year produces 600 lbs. of sago,
which word, in the language of the Papuas, signifies _bread_, being
the staple food of the islanders. To obtain it, the tree must be cut
down, and the stem divided into pieces, from which the flour is beaten
and washed out[I]. After being cut down, the vegetative power still
remains in the root, which again forms a trunk, and this proceeds
through its different stages, until it is again subjected to the axe,
and made to yield its alimentary contents for the service of man. Nor
is the extraordinary productiveness of a single tree the only point
worthy of notice, for, being endogenous plants, devoid of branches, an
unusual number of them can grow in a small space. Mr. Craufurd
calculates that an English acre could contain four hundred and
thirty-five sago trees, which would yield one hundred and twenty
thousand five hundred pounds avoirdupois of starch, being at the rate
of more than eight thousand pounds yearly. Besides the farina or meal,
every tree cut down furnishes, in its terminal bud, a luxury which is
as much prized as that of the _areca oleracea_, or cabbage palm of the
West Indies, and which is eaten either raw as a salad, or cooked.
Further, the leaves afford so excellent a material for covering
houses, that even in those hot and humid parts of the world, where
decomposition goes on so rapidly, it does not require to be renewed
oftener than once in seven years.
The _Mauritia flexuosa_, or fan palm of the Oronooco, is of still
greater utility to the natives of South America. It is a social palm,
abounding in the marshes, and having a geographical range of very vast
extent. The whole northern portion of South America, east of the
Cordilleras, appears to be possessed of this gorgeous palm; from the
mouth of the Oronooco to the river Amazon, and through the whole of
Guiana, through Surinam and the northern part of Brazil, and in very
various places along the river Amazon, even to its source on the
eastern declivity of the Cordilleras, this palm is found, constituting
forests of greater or less extent. Its smooth grey stem rising often
100 feet, forms groups that, in the northern part of Brazil, resemble
the pallisades of some gigantic fortress. The produce of these lofty
cylinders is very great, not merely of sago, which is procured only
when the process of flowering is about to occur, but many trees being
cut down before this event, a juice is obtained from them, which
forms, by fermentation, a sweet wine; while those that flower, after
which no good sago can be got, furnish an extraordinary quantity of
fruit, hanging in bunches many feet in length, which is as agreeable
as ripe apples, the taste of which it resembles. The other products of
this tree are numerous[J].
It would lead beyond just limits, were we to notice in detail, the
plants which yield starch suitable for food, only after undergoing a
process of art, by which an acrid principle is driven off, and a
bland, wholesome substance remains behind. Such is the Janipha (or
Jatropha) Manihot, which yields the Mandiocca, Tapioca, or Cassava, an
article not only of great consumption in, but also of considerable
export from, Brazil (see Spix and Martius' Travels, and Lib. of Enter.
Knowledge, Vegt. Sub. Food of Man, p. 152), which, when raw, is
poisonous both to man and cattle, though it becomes safe and agreeable
by the application of heat. So likewise the large tubers of several
_Arums_, such as _A. Macrorhizon_, _A. Colocasia_, _Caladium acre_,
and which are cultivated with great care in tropical and subtropical
countries, particularly in the Sandwich and South Sea islands. All of
these excite inflammation and swelling of the mouth and tongue, even
to the danger of suffocation, but which are disarmed of their
virulence, and converted into an article of daily consumption, by
fire. Even yams and sweet potatoes, which are naturally mild, are less
articles of consumption in the south sea islands, than the Tarro, as
these tubers of the _arums_ are designated.
I omit all other plants to fix attention on the potatoe, which is not
only the source of the purest starch of all, but has many interesting
points connected with its history and habitudes, peculiarly connected
with my subject. No plant has contributed more to banish those famines
which were formerly of so frequent occurrence in Europe, and all the
dire train of suffering and disease consequent upon them. Yet did it,
in many instances, require royal edicts to induce some nations to
cultivate what is now regarded as one of the prime blessings of
Providence, from nearly one end of the earth to the other; the potatoe
being raised from Hammerfest, in Lapland, lat. 71 deg. north, through all
Europe, the plains of India, in China, Japan, the south-sea islands,
New Holland, even to New Zealand. What renders it so peculiarly
valuable is, that in the seasons when the corn crop fails, that of
potatoes is generally more abundant; thus furnishing a substitute for
the other, which proves defective from atmospheric conditions, which
have little influence over the potatoe, placed as it is underground,
and secure against extremes of temperature. The potatoe is not a root,
as commonly supposed, but an underground collection of buds, having a
quantity of starch accumulated around them, for their nourishment when
they begin to grow. The quantity of starch varies greatly with the
kind of potatoe cultivated, the mode of cultivation, the time of
setting, and above all, with the season of the year when the analysis
is made. Potatoes in general, afford from one-fifth to one-seventh
their weight of dry starch[K]; besides some other nutritive materials.
The quantity of starch seems to be at its maximum in the winter months;
as 100 pounds of potatoes yield in August about 10 lbs., in October
nearly 15 lbs., in November to March 17 lbs., in April 133/4 lbs., and
in May 10 lbs. Nor is the quantity of starch alone diminished in
spring, but the nitrogen which belongs to some of the other nutritive
principles, likewise suffers a deduction; as fresh, not dried
potatoes, contain 0.0037 per cent. of azote, while potatoes ten months
old contain only 0.0028, causing a sensible difference in their power
of imparting nourishment. The starch is withdrawn from the tubers of
the potatoe, precisely in the same way that it is transferred from the
root, stem, or seeds of other plants, for the service of the young
shoot; but the mode in which it is accomplished is but of recent
discovery, and constitutes one of the most beautiful instances of
design which the whole vegetable kingdom can unfold; "that man's
scepticism must be incurable who does not perceive, and acknowledge,
that the means now to be detailed were created for the express
accomplishment of the ends[L]."
Starch has been described above as consisting of a multitude of little
cells or vesicles, having an envelope, insoluble in water, formed of a
kind of organized membrane, and containing within it a substance which
is soluble in water, termed amidin. This soluble material is the
nutritive element on which the young shoot, proceeding from every eye
or bud of the potatoes, is to subsist, till it has developed roots,
and unfolded its leaves to prepare additional alimentary substance.
But if this soluble material be enclosed in an insoluble membrane, how
are the contents to be made available for the growth of the plant? It
is true, indeed, that water of the temperature of 160 deg. Fahr. can
rupture this tegument, as occurs in the process of boiling potatoes;
but the water diffused through the earth in the neighbourhood of the
growing tuber, never reaches such a height. How then is the difficulty
obviated? This is effected by a secretion called _diastase_ which is
found in the tubers in the immediate vicinity of the eyes or buds. "It
is stored up in that situation for the purpose of being conveyed, by
the vessels connected with the bud, into the substance of the tuber,
when the demand for nutrition is occasioned by the development of the
shoot. It is probable that the secretion of _diastase_ takes place in
every instance in which starch previously deposited is to be
re-absorbed[M]." It is not to be found before grains or tubers begin
to sprout, yet, "such is its energy, that one part of it is sufficient
to render soluble the interior portion of two thousand parts of
starch, and to convert it into sugar[N]." Strong as is the analogy
between starch and gum, yet _diastase_ does not convert gum into
sugar; the one being as completely soluble as the other, its
intervention is clearly unnecessary. Neither does it act on sugar. It
is found, and exerts its powers, only where it is required. Nor does
it come into play one moment before the necessity for it occurs. While
the potatoe is in its state of winter repose, and no vegetative
process going on, the elements of which the _diastase_ is formed, are
equally quiescent, but no sooner does the season recur when an
augmented temperature rouses the slumbering energy of the tuber, than
this potent principle exhibits its efficacy, and changes the insoluble
starch into the nutritious sugar. Who, that can read, or reading
reflect and ponder on these things, but must conclude that the laws
which regulate the whole actions were impressed upon their subjects by
a Creator infinite in design, in wisdom, and in power? If such insight
into his doings are permitted to us now, what may we not hope for when
we no longer "see as through a glass darkly[O]?"
The insolubility of the starch in cold water, affords a convenient
means of separating the flour from the other materials, by which it
may be abstracted from the tubers when in the greatest abundance, and
be preserved unchanged for the use of man. This is done by simply
rasping down the potatoes over a seirce, and passing a current of
water over the raspings. The water passes through the seirce milky
from the starch suspended in it. The starch is allowed to fall to the
bottom, and is two or three times washed with pure water; it is then
allowed to dry[P]. If this process be followed in the winter months,
when the quantity of starch is greatest, the result is, a sixth
portion of the weight of the potatoes employed, in a condition fit not
only for immediate use, but capable of preservation for years. "To
those who live solely, or even principally, on potatoes, it must be of
immense importance to have the nutritious part preserved when in its
greatest perfection, instead of leaving it exposed to injury,
decomposition, or decay[Q]."
It is unnecessary to enlarge upon the sources of starch and its
obvious utility to mankind. Previous to its being consumed by the
plant in which it is amassed, it is by various means, but chiefly by
diastase, transformed into sugar. Following this natural transition, I
shall next consider sugar as an article of diet. In temperate
climates, sugar is regarded as a luxury, one indeed which is nearly
indispensable, but in tropical countries it is a universal article of
subsistence, partly as real sugar, and partly, and more generally, as
it occurs in the cane. It is inconceivable what enormous quantities of
the sugar-cane is consumed in this way; vast ship-loads arrive daily
in the market at Manilla, and in Rio Janiero; in the Sandwich Islands
and other places, every child is seen going about with a portion of
sugar-cane in the hand. It has been called "the most perfect
alimentary substance in nature," and the results, in the appearance of
the negroes, during the cane-harvest, notwithstanding the increased
severe toils of that season, seem to confirm the statement. They
almost invariably become plump, and sleek, and scarcely take any other
food while the harvest lasts; even the sickly revive, and often
recover their health.
The chief source of sugar is large grass (_saccharum officinarum_), of
which there are several varieties, differing essentially in
productiveness, but the best of which is the Otaheita cane, the stem
of which is higher, thicker, and more succulent than the Creole cane,
and which yields not only one-third more of juice than the Creolian
cane on the same space of land; but from the thickness of its stem,
and the tenacity of its ligneous fibres, it furnishes much more fuel.
One variety was known in India, in China, and all the islands of the
Pacific ocean, from the most remote antiquity; it was planted in
Persia, in Chorasan, as early as the fifth century of our era, in
order to obtain from it solid sugar. The Arabs carried this reed--so
useful to the inhabitants of hot and temperate countries--to the
shores of the Mediterranean. In 1306, its cultivation was yet unknown
in Sicily, but was already common in the island of Cyprus, at Rhodes,
and in the Morea. A hundred years after it enriched Calabria, Sicily,
and the coasts of Spain. From Sicily the Infant Henry transplanted the
cane to Madeira; and from Madeira it passed to the Canary islands. It
was thence transplanted to St. Domingo, in 1513, and has since spread
to the continent of South America, and to the West Indies, whence the
chief supply for Europe is obtained.
The vast circuit which it has described in these successive
transplantations attest the sense which mankind had of the benefits it
bestowed in its course. The introduction of the Otaheita cane is
another proof of the obligations which modern times are under to
navigation, as we owe this plant to the voyages of Bougainville, Cook,
and Bligh[R].
The sugar-cane requires for its perfection, a temperature of
considerable elevation, and succeeds best where the mean temperature
is 24 deg. or 25 deg. (of the centigrade thermometer), yet it will
prosper, though with less produce, where it only reaches 19 deg. or 20
deg. (centigrade). Its cultivation extends from the verge of the ocean,
where the canes are often washed by the waves[S], to localities on the
mountains 3,000 feet above the sea; and even in the extensive plains
of Mexico and Colombia, where, from the reflection of the sun's rays
the heat is greatly increased, to 4,000, 5,000, 6,000, though the mean
temperature of the city of Mexico be only 17 deg. (centigrade), yet sugar
is procured at 6,600 feet.
The fertility and productiveness of the sugar-cane is immense, second
only to the sago-palms. "The first sugar-canes planted with care on a
virgin soil, yield a harvest during twenty to twenty-five years, after
which they must be replanted every three years." In the island of
Cuba, instances are known of a sugar-plantation existing for
forty-five years. To procure new plants, the tedious process of sowing
seeds is not necessary. The practice is followed of taking cuttings,
and the stools, or scions, which spring from the joints (_nodi_) of
the old plant, are fit to be separated in fourteen days; these, in the
course of a year, are so well grown that they may be cut down, and
submitted to the sugar-mill. An English acre under culture for sugar,
in Java, yields 1285 pounds avoirdupois of refined sugar, and the
produce at Cuba is nearly the same.
Let not the thought arise, on the perusal of these statements, that
the gifts of Providence are distributed with partiality, as nothing
could be more unfounded. Independent of the destruction of the
plantations which tropical hurricanes so often occasion, an insect of
the locust kind, more particularly in the East Indies, produces such
fearful devastation as to realize the scene described by the prophet
Joel--"A fire devoureth before them, and behind them a flame burneth:
the land is as the garden of Eden before them, and behind them a
desolate wilderness; yea, and nothing shall escape them[T]." From such
visitations, northern latitudes are generally exempt, and the constant
struggle which man has had to maintain with the elements and a
churlish soil, has so whetted his faculties as to render the return
for his labour not only more certain, but even more abundant[U].
As if to shew that "the earth full of the riches of the Lord," in
parts of the world where the low temperature is an obstacle to the
profitable cultivation of the sugar-cane, a substitute is found for it
in the _acer saccharinum_, or sugar-maple, which presents the great
peculiarity of the ascending sap being charged with sugar to such a
degree as to be then fit for the manufacture of this valuable
substance. There results from this circumstance a most important
advantage to the inhabitants of the northern regions, where this tree
grows, that the juice is extracted early in spring, a time when the
rigour of the season condemns the labourer to inactivity. Besides, the
sugar-maple grows spontaneously, and requires no care, till it is fit
for tapping; and when deprived of its juice, and incapable of yielding
more sugar, its wood is applicable to a far greater number and variety
of uses than the bruised cane, since as fuel the maple is most
valuable; and its ashes yield, from their richness in the alkaline
principle, four-fifths of the potash exported to Europe from Boston
and New York. The timber of the sugar-maple is also highly prized,
both for common and ornamental purposes--as the beautiful bird's-eye
maple is obtained from this tree.
"The sugar-maple begins a little north of Lake St. John, in Canada,
near 48 deg. of north lat., which, in the rigour of its winter,
corresponds to 68 deg. of Europe. It is nowhere more abundant than
between 46 deg. and 43 deg. of north lat., which space comprises Canada,
New Brunswick, Nova Scotia, the states of Vermont and New Hampshire, and
the district of Maine. Farther south, it is common only in Genessee,
in the state of New York, and in the upper parts of Pennsylvania. It
is estimated by Dr. Rush, that in the northern part of these two
states, there are 10,000,000 acres which produce these trees in the
proportion of thirty to an acre. The process of making maple-sugar is
commonly begun in February, or in the beginning of March, while the
cold continues intense, and the ground is still covered with snow. The
sap begins to be in motion at this season, two months before the
general revival of vegetation. The sap continues to flow for six
weeks; after which it becomes less abundant, less rich in saccharine
matter, and sometimes even incapable of crystallization. In this case
it is consumed in the state of molasses; or exposed for three or four
days to the sun, when it is converted into vinegar by the acetous
fermentation: a kind of beer is also made of it. The amount of sugar
produced by each tree in a year varies from different causes. The
yearly product varies from 2 lbs. to 4 lbs. for each tree[V]." The sap
is most abundant from young trees, but less charged with sugar. The
average produce is five per cent. of sugar. The richer the sap is in
saccharine matter, it is so much the more profitable to extract it, as
in such a case it is nearly pure from all mucilaginous matter, or free
acid, and may be consolidated by the action of cold alone by merely
freezing it, thus rendering boiling unnecessary.
Sugar exists in many other plants, such as the beet-root, from which
it is extracted; and also the stem of the maize, or Indian corn, is
charged with an extraordinary quantity of sugar, and it may either be
brought to the state of a honey-like sugar, or the juice pressed out
of the stalk, and fermented, forming the _pulque de mahio_, or _pulque
de Flaolli_, in Mexico[W].
Gum has been already stated to be the basis of all the other
organizable products, and it is found not only in almost all plants,
but in nearly all parts of them. In a pure or nearly isolated state,
it exists chiefly in the inner bark of vascular and especially
exogenous trees, and is preserved in the interior with the greatest
care: its escape externally results either from disease, as in the
case of plum and cherry-trees, from the puncture of insects, cracks in
the bark, or by artificial incisions. The death of the tree soon
follows the loss of this important juice, and thousands of trees of
the genus acacia are annually sacrificed in different parts of Africa
to procure the gum-arabic of commerce. It is only in a few genera and
tribes of trees, that it exists in so concentrated a state as to
assume the solid form on exposure to the air, but in some of these the
quantity is amazing. Hot countries are the chief abodes of such trees.
Thus, besides the immense quantity obtained from the acacias, the
_anacardium occidentale_ (cashew-nut tree) in America, has furnished
from a single tree a mass weighing forty-two pounds. Gum is mawkish,
insipid, and generally unpalatable, yet highly nutritive; and the
Africans, during the harvest of gum at Senegal, live entirely upon it,
eight ounces being the daily allowance for each man. In general they
become plump on this fare; and such should be the result, if the
calculation be correct, which assigns as great nutritive power to four
ounces of gum as to one pound of bread. This concentration of
nourishment renders gum a peculiarly suitable food for lengthened
journeys through the deserts, as it occupies small compass, and a
little suffices to stay the cravings of hunger. Thus, upwards of a
thousand persons may occupy more than two months in a journey from
Abyssinia to Cairo without any other kind of food[X]. Its bland,
demulcent properties fit it to correct the acrimony of the secretions
formed under the influence of a tropical sun and torrid air, with a
scanty and irregular supply of water. Plants, likewise, are preserved
in a vegetative and living state, mid sandy and arid wastes, by the
quantity of gum stored up in them. Hence succulent plants, such as
cacti and others, may be found in the steppes and sandy plains of
South America, verdant and healthy, though no rain may fall to convey
fresh sap into them for months, or even a year. In the form of
mucilage, _i. e._, gum in a state of solution, it is found in a very
large number of plants, and thus contributes to the maintenance of man
and animals. In these it is generally associated with some other
principles, which render it either more palatable or more easily
digested. A very large number of our esculent vegetables owe their
nutritive properties to the gummy matters with which they abound, and
the favour with which they are regarded to the other matters united
with it. Those which have a bitter principle are very excellent, when
this is in small proportion; and as, in most of them, the gummy matter
is prepared first, requiring for its formation only a moderate degree
of light and heat, while the bitter, or other principle, is added at a
later period, under the influence of stronger light; such plants, when
young, are tender and agreeable; nay, even very poisonous plants, when
very young, are wholesome and pleasant, which, at a more advanced
season, are virose and disagreeable. Thus, the peasantry of France and
Piedmont eat the young crowfoots (ranunculus) and poppies, after
boiling them, and find them safe and nourishing. The same result
follows exclusion of light, as in the process of blanching, by which
means celery, sea-kale, and other vegetables, are rendered esculent,
which in the wild state are poisonous or repulsive. In northern
latitudes, the light being intense for a short time only, many plants
are used there which, in the southern, are dangerous or destructive,
such as hemlock and monkshood. A moderate degree of bitterness is a
very useful accompaniment of the gum, which alone is cloying and even
oppressive to the stomach. The presence of a bitter principle in many
lichens promotes their digestion, and thus even the tough and leathery
ones, called tripe of the rocks, can be eaten, and sustain life amid
great privations and sufferings. The rein-deer moss (_cludonia
rangiferina_) is another lichen of great utility: it is not much
employed as human food, but it is the main support of the rein-deer
for a great portion of the year, and thus renders Lapland a fit abode
for man.
A peculiar modification of gum constitutes _pectine_ or vegetable
jelly; and this occurs in fruits, such as the orange, currant, and
gooseberry, &c., also in many of the algae or sea-weeds, which are, or
ought to be, much employed as a delicate article of nourishment. The
edible swallow's nest, so greatly esteemed by the Chinese, is an alga,
gathered by the birds. The Ceylon moss (_Gigartina lichenoides_), and
the carrageen or Irish moss (_Chondrus crispus_), with many others,
might be made to contribute largely to the subsistence of man. Not
merely earth, from its fruitful bosom, but the vast ocean, offer their
rich produce to nourish and sustain the only intelligent occupant of
the globe, who should ever remember the declaration of the psalmist,
"O Lord! how manifold are thy works! in wisdom hast thou made them
all: the earth is full of thy riches; so is the great and wide sea!"
(Ps. civ.)