FRUCTOSE, LAEVULOSE, or FRUIT-SUGAR, a carbohydrate of the formula
C6H12O6. It is closely related to ordinary d-glucose, with which it
occurs in many fruits, starches and also in honey. It is a hydrolytic
product of inulin, from which it may be prepared; but it is more usual
to obtain it from "invert sugar," the mixture obtained by hydrolysing
cane sugar with sulphuric acid. Cane sugar then yields a syrupy mixture
of glucose and fructose, which, having been freed from the acid and
concentrated, is mixed with water, cooled in ice and calcium hydroxide
added. The fructose is precipitated as a saccharate, which is filtered,
suspended in water and decomposed by carbon dioxide. The liquid is
filtered, the filtrate concentrated, and the syrup so obtained washed
with cold alcohol. On cooling the fructose separates. It may be obtained
as a syrup, as fine, silky needles, a white crystalline powder, or as a
granular crystalline, somewhat hygroscopic mass. When anhydrous it melts
at about 95 deg. C. It is readily soluble in water and in dilute alcohol,
but insoluble in absolute alcohol. It is sweeter than cane sugar and is
more easily assimilated. It has been employed under the name diabetin as
a sweetening agent for diabetics, since it does not increase the
sugar-content of the urine; other medicinal applications are in phthisis
(mixed with quassia or other bitter), and for children suffering from
tuberculosis or scrofula in place of cane sugar or milk-sugar.
Chemically, fructose is an oxyketone or ketose, its structural formula
being CH2OH.(CH.OH)3.CO.CH2OH; this result followed from its conversion
by H. Kiliani into methylbutylacetic acid. The form described above is
_laevo_-rotatory, but it is termed d-fructose, since it is related to
d-glucose. Solutions exhibit mutarotation, fresh solutions having a
specific rotation of -104.0 deg., which gradually diminishes to -92 deg.
It was synthesized by Emil Fischer, who found the synthetic sugar which
he named [alpha]-acrose to be (d + l)-fructose, and by splitting this
mixture he obtained both the d and l forms. Fructose resembles d-glucose
in being fermentable by yeast (it is the one ketose which exhibits this
property), and also in its power of reducing alkaline copper and silver
solutions; this latter property is assigned to the readiness with which
hydroxyl and ketone groups in close proximity suffer oxidation. For the
structural (stereochemical) relations of fructose see SUGAR.
FRUGONI, CARLO INNOCENZIO MARIA (1692-1768), Italian poet, was born at
Genoa on the 21st of November 1692. He was originally destined for the
church and at the age of fifteen, in opposition to his strong wishes,
was shut up in a convent; but although in the following year he was
induced to pronounce monastic vows, he had no liking for this life. He
acquired considerable reputation as an elegant writer both of Latin and
Italian prose and verse; and from 1716 to 1724 he filled the chairs of
rhetoric at Brescia, Rome, Genoa, Bologna and Modena successively,
attracting by his brilliant fluency a large number of students at each
university. Through Cardinal Bentivoglio he was recommended to Antonio
Farnese, duke of Parma, who appointed him his poet laureate; and he
remained at the court of Parma until the death of Antonio, after which
he returned to Genoa. Shortly afterwards, through the intercession of
Bentivoglio, he obtained from the pope the remission of his monastic
vows, and ultimately succeeded in recovering a portion of his paternal
inheritance. After the peace of Aix-la-Chapelle he returned to the court
of Parma, and there devoted the later years of his life chiefly to
poetical composition. He died on the 20th of December 1768. As a poet
Frugoni was one of the best of the school of the Arcadian Academy, and
his lyrics and pastorals had great facility and elegance.
His collected works were published at Parma in 10 vols. in 1799, and a
more complete edition appeared at Lucca in the same year in 15 vols. A
selection from his works was published at Brescia in 1782, in 4 vols.
FRUIT (through the French from the Lat. _fructus_; _frui_, to enjoy), in
its widest sense, any product of the soil that can be enjoyed by man or
animals; the word is so used constantly in the Bible, and extended, as a
Hebraism, to offspring or progeny of man and of animals, in such
expressions as "the fruit of the body," "of the womb," "fruit of thy
cattle" (Deut. xxviii. 4), &c., and generally to the product of any
action or effort. Between this wide and frequently figurative use of the
word and its application in the strict botanical sense treated below,
there is a popular meaning, regarding the objects denoted by the word
entirely from the standpoint of edibility, and differentiating them
roughly from those other products of the soil, which, regarded
similarly, are known as vegetables. In this sense "fruit" is applied to
such seed-envelopes of plants as are edible, either raw or cooked, and
are usually sweet, juicy or of a refreshing flavour. But applications of
the word in this sense are apt to be loose and shifting according to the
fashion of the time.
Fruit, in the botanical sense, is developed from the flower as the
result of fertilization of the ovule. After fertilization various
changes take place in the parts of the flower. Those more immediately
concerned in the process, the anther and stigma, rapidly wither and
decay, while the filaments and style often remain for some time; the
floral envelopes become dry, the petals fall, and the sepals are either
deciduous, or remain persistent in an altered form; the ovary becomes
enlarged, forming the _pericarp_; and the ovules are developed as the
seeds, containing the embryo-plant. The term fruit is strictly applied
to the mature pistil or ovary, with the seeds in its interior; but it
often includes other parts of the flower, such as the bracts and floral
envelopes. Thus the fruit of the hazel and oak consists of the ovary
enveloped by the bracts; that of the apple and pear, of the ovary and
floral receptacle; and that of the pine-apple, of the whole
inflorescence. Such fruits are sometimes distinguished as _pseudocarps_.
In popular language, the fruit includes all those parts which exhibit a
striking change as the result of fertilization. In general, the fruit is
not ripened unless fertilization has been effected; but cases occur as
the result of cultivation in which the fruit swells and becomes to all
appearance perfect, while no seeds are produced. Thus, there are
seedless oranges, grapes and pineapples. When the ovules are
unfertilized, it is common to find that the ovary withers and does not
come to maturity; but in the case of bananas, plantains and bread-fruit,
the non-development of seeds seems to lead to a larger growth and a
greater succulence of fruit.
The fruit, like the ovary, may be formed of a single carpel or of
several. It may have one cell or cavity, being _unilocular_; or many,
_multilocular_, &c. The number and nature of the divisions depend on
the number of carpels and the extent to which their edges are folded
inwards. The appearances presented by the ovary do not always remain
permanent in the fruit. Great changes are observed to take place, not
merely as regards the increased size of the ovary, its softening or
hardening, but also in its internal structure, owing to the
suppression, additional formation or enlargement of parts. Thus, in
the ash (fig. 1) an ovary with two cells, each containing an ovule
attached to a central placenta, is changed into a unilocular fruit
with one seed; one ovule becomes abortive, while the other, g,
gradually enlarging until the septum is pushed to one side, unites
with the walls of the cell, and the placenta appears to be parietal.
In the oak and hazel, an ovary with three and two cells respectively,
and two ovules in each, produces a one-celled fruit with one seed. In
the coco-nut, a trilocular and triovular ovary produces a one-celled,
one-seeded fruit. This abortion may depend on the pressure caused by
the development of certain ovules, or it may proceed from
non-fertilization of all the ovules and consequent non-enlargement of
the carpels. Again, by the growth of the placenta, or the folding
inwards of parts of the carpels, divisions occur in the fruit which
did not exist in the ovary. In _Cathartocarpus Fistula_ a one-celled
ovary is changed into a fruit having each of its seeds in a separate
cell, in consequence of spurious dissepiments being produced
horizontal from the inner wall of the ovary. In flax (_Linum_) by the
folding inwards of the back of the carpels a five-celled ovary becomes
a ten-celled fruit. In _Astragalus_ the folding inwards of the dorsal
suture converts a one-celled ovary into a two-celled fruit; and in
_Oxytropis_ the folding of the ventral suture gives rise to a similar
change. The development of cellular or pulpy matter, and the
enlargement of parts not forming whorls of the flower, frequently
alter the appearance of the fruit, and render it difficult to discover
its formation. In the gooseberry (fig. 29), grape, guava, tomato and
pomegranate, the seeds nestle in pulp formed by the placentas. In the
orange the pulpy matter surrounding the seeds is formed by succulent
cells, which are produced from the inner partitioned lining of the
pericarp. In the strawberry the receptacle becomes succulent, and
bears the mature carpels on its convex surface (fig. 2); in the rose
there is a fleshy hollow receptacle which bears the carpels on its
concave surface (fig. 3). In the juniper the scaly bracts grow up
round the seeds and become succulent, and in the fig (fig. 4) the
receptacle becomes succulent and encloses an inflorescence.
[Illustration:
Fig. 1.--Samara or winged fruit of Ash (_Fraxinus_). 1, Entire, with
its wing a; 2, lower portion cut transversely, to show that it
consists of two cells; one of which, l, is abortive, and is reduced
to a very small cavity, while the other is much enlarged and filled
with a seed g.
Fig. 2.--Fruit of the Strawberry (_Fragaria vesca_), consisting of
an enlarged succulent receptacle, bearing on its surface the small
dry seed-like fruits (achenes). (After Duchartre.)
From Strasburger's _Lehrbuch der Botanik_, by permission of Gustav
Fischer.
Fig. 3.--Fruit of the Rose cut vertically. s', Fleshy hollowed
receptacle; s, persistent sepals; _fr_, ripe carpels; e, stamens,
withered.
Fig. 4.--Peduncle of Fig (_Ficus Carica_), ending in a hollow
receptacle enclosing numerous male and female flowers.
Fig. 5.--Fruit of Cherry (_Prunus Cerasus_) in longitudinal section.
ep, Epicarp; m, mesocarp; en, endocarp.
From Strasburger's _Lehrbuch der Botanik_, by permission of Gustav
Fischer.]
The pericarp consists usually of three layers, the external, or
_epicarp_ (fig. 5, ep); the middle, or _mesocarp_, m; and the
internal, or _endocarp_, _en_. These layers are well seen in such a
fruit as the peach, plum or cherry, where they are separable one from
the other; in them the epicarp forms what is commonly called the skin;
the mesocarp, much developed, forms the flesh or pulp, and hence has
sometimes been called _sarcocarp_; while the endocarp, hardened by the
production of woody cells, forms the _stone_ or _putamen_ immediately
covering the kernel or seed. The pulpy matter found in the interior of
fruits, such as the gooseberry, grape and others, is formed from the
placentas, and must not be confounded with the sarcocarp. In some
fruits, as in the nut, the three layers become blended together and
are indistinguishable. In bladder senna (_Colutea arborescens_) the
pericarp retains its leaf-like appearance, but in most cases it
becomes altered both in consistence and in colour. Thus in the date
the epicarp is the outer brownish skin, the pulpy matter is the
mesocarp or sarcocarp, and the thin papery-like lining is the endocarp
covering the hard seed. In the medlar the endocarp becomes of a stony
hardness. In the melon the epicarp and endocarp are very thin, while
the mesocarp forms the bulk of the fruit, differing in texture and
taste in its external and internal parts. The rind of the orange
consists of epicarp and mesocarp, while the endocarp forms partitions
in the interior, filled with pulpy cells. The part of the pericarp
attached to the peduncle is the base, and the point where the style or
stigma existed is the apex. This latter is not always the apparent
apex, as in the case of the ovary; it may be lateral or even basilar.
The style sometimes remains in a hardened form, rendering the fruit
_apiculate_; at other times it falls off, leaving only traces of its
existence. The presence of the style or stigma serves to distinguish
certain single-seeded pericarps from seeds.
[Illustration:
FIG. 6.--Seed-vessel or capsule of Campion, opening by ten teeth at
the apex. The calyx c is seen surrounding the seed-vessel.
FIG. 7.--Capsule of Poppy, opening by pores p, under the radiating
peltate stigma s.]
Dehiscence of fruits.
When the fruit is mature and the seeds are ripe, the carpels usually
give way either at the ventral or dorsal suture or at both, and so
allow the seeds to escape. The fruit in this case is _dehiscent_. But
some fruits are _indehiscent_, falling to the ground entire, and the
seeds eventually reaching the soil by their decay. By dehiscence the
pericarp becomes divided into different pieces, or _valves_, the fruit
being univalvular, bivalvular or multivalvular, &c., according as
there are one, two or many valves. The splitting extends the whole
length of the fruit, or is partial, the valves forming teeth at the
apex, as in the order Caryophyllaceae (fig. 6). Sometimes the valves
are detached only at certain points, and thus dehiscence takes place
by pores at the apex, as in poppy (fig. 7), or at the base, as in
_Campanula_. Indehiscent fruits are either dry, as the nut, or fleshy,
as the cherry and apple. They are formed of one or several carpels. In
the former case they usually contain only a single seed, which may
become so incorporated with the pericarp as to appear to be naked, as
in the grain of wheat and generally in grasses. In such cases the
presence of the remains of style or stigma determines their true
nature.
[Illustration:
FIG. 8.--Dry dehiscent fruit. The pod (legume) of the Pea; r, the
dorsal suture; b, the ventral; c, calyx; s, seeds.
From Vines' _Students' Text-Book of Botany_, by permission of Swan
Sonnenschein & Co.
FIG. 9.--(1) Fruit or capsule of Meadow Saffron (_Colchicum
autumnale_), dehiscing along the septa (septicidally); (2) same cut
across, showing the three chambers with the seeds attached along the
middle line (axile placentation).
FIG. 10.--Diagram to illustrate the septicidal dehiscence in a
pentalocular capsule. The loculaments l correspond to the number of
the carpels, which separate by splitting through the septa, s.
FIG. 11.--The seed vessel (capsule) of the Flower-de-Luce (_Iris_),
opening in a loculicidal manner. The three valves bear the septa in
the centre, and the opening takes place through the back of the
loculaments. Each valve is formed by the halves of contiguous
carpels.
FIG. 12.--Diagram to illustrate loculicidal dehiscence. The
loculaments l, split at the back, and the valves separate, bearing
the septa s on their centres.
FIG. 13.--Diagram to illustrate septifragal dehiscence, in which the
dehiscence takes place through the back of the loculaments l, and
the valves separate from the septa s, which are left attached to the
placentas in the centre.]
Dehiscent fruits, when composed of single carpels, may open by the
ventral suture only, as in the paeony, hellebore, _Aquilegia_ (fig.
28) and _Caltha_; by the dorsal suture only, as in magnolias and some
_Proteaceae_, or by both together, as in the pea (fig. 8) and bean; in
these cases the dehiscence is _sutural_. When composed of several
united carpels, two types of dehiscence occur--a longitudinal and a
transverse. In the longitudinal the separation may take place by the
dissepiments throughout their length, so that the fruit is resolved
into its original carpels, and each valve represents a carpel, as in
rhododendron, _Colchicum_, &c.; this dehiscence, in consequence of
taking place through the septum, is called _septicidal_ (figs. 9, 10).
The valves separate from their commissure, or central line of union,
carrying the placentas with them, or they leave the latter in the
centre, so as to form with the axis a column of a cylindrical, conical
or prismatic shape. Dehiscence is _loculicidal_ when the union between
the edges of the carpels is persistent, and they dehisce by the dorsal
suture, or through the back of the loculaments, as in the lily and
iris (figs. 11, 12). In these cases each valve consists of a half of
each of two contiguous carpels. The placentas either remain united to
the axis, or they separate from it, being attached to the septa on the
valves. When the outer walls of the carpels break off from the septa,
leaving them attached to the central column, the dehiscence is said to
be _septifragal_ (fig. 13), and where, as in _Linum catharticum_ and
_Calluna_, the splitting takes place first of all in a septicidal
manner, the fruit is described as _septicidally septifragal_; while in
other cases, as in thorn apple (_Datura Stramonium_), where the
splitting is at first loculicidal, the dehiscence is _loculicidally
septifragal_. In all those forms the separation of the valves takes
place either from above downwards or from below upwards. In
_Saxifraga_ a splitting for a short distance of the ventral sutures of
the carpels takes place, so that a large apical pore is formed. In the
fruit of Cruciferae, as wallflower (fig. 14), the valves separate from
the base of the fruit, leaving a central _replum_, or frame, which
supports the false septum formed by a prolongation from the parietal
placentas on opposite sides of the fruit, extending between the
ventral sutures of the carpels. In Orchidaceae (fig. 15) the pericarp,
when ripe, separates into three valves in a loculicidal manner, but
the midribs of the carpels, to which the placentas are attached, often
remain adherent to the axis both at the apex and base after the valves
bearing the seeds have fallen. The other type of dehiscence is
transverse, or _circumscissile_, when the upper part of the united
carpels falls off in the form of a lid or operculum, as in _Anagallis_
and in henbane (_Hyoscyamus_) (fig. 16).
[Illustration:
FIG. 14.--Siliqua or seed-vessel of Wallflower (_Cheiranthus
Cheiri_), opening by two valves, which separate from the base
upwards, leaving the seeds attached to the dissepiment which is
supported by the replum.
From Strasburger's _Lehrbuch der Botanik_, by permission of Gustav
Fischer.
FIG. 15.--Capsule of an Orchid (_Xylobium_). v, valve.
FIG. 16.--Seed-vessel of _Anagallisarvensis_, opening by
circumscissile dehiscence.
From Strasburger's _Lehrbuch der Botanik_, by permission of Gustav
Fischer.
FIG. 17.--Lomentum of _Hedysarum_ which, when ripe, separates
transversely into single-seeded portions or mericarps.