Part 4

Sometimes there is an additional covering to the seed, formed after fertilization, to which the name _arillus_ has been given (fig. 38). This is seen in the passion-flower, where the covering arises from the placenta or extremity of the funicle at the base of the ovule and passes upwards towards the apex, leaving the micropyle uncovered. In the nutmeg and spindle tree this additional coat is formed from above downwards, constituting in the former case a laciniated scarlet covering called _mace_. In such instances it has been called an _arillode_ (fig. 39). This arillode, after growing downwards, may be reflected upwards so as to cover the micropyle. The fleshy scarlet covering formed around the naked seed in the yew is by some considered of the nature of an aril. On the testa, at various points, there are produced at times other cellular bodies, to which the name of _strophioles_, or _caruncles_, has been given, the seeds being strophiolate or carunculate. These tumours may occur near the base of the seed, as in _Polygala_, or at the apex, as in Castor-oil plant (_Ricinus_); or they may occur in the course of the raphe, as in blood-root (_Sanguinaria_) and _Asarabacca_. The funicles of the ovules frequently attain a great length in the seed, and in some magnolias, when the fruit dehisces, they appear as long scarlet cords suspending the seeds outside. The hilum or umbilicus of the seed is usually well marked, as a scar of varying size; in the calabar bean and in some species of Mucuna and Dolichos it extends along a large portion of the edge of the seed; it frequently exhibits marked colours, being black in the bean, white in many species of Phaseolus, &c. The micropyle (fig. 35, m) of the seed may be recognizable by the naked eye, as in the pea and bean tribe, _Iris_, &c., or it may be very minute or microscopic. It indicates the true apex of the seed, and is important as marking the point to which the root of the embryo is directed. At the micropyle in the bean is observed a small process of integument, which, when the young plant sprouts, is pushed up like a lid; it is called the _embryotega_. The chalaza (fig. 38, ch) is often of a different colour from the rest of the seed. In the orange (fig. 40) it is of a reddish-brown colour, and is easily recognized at one end of the seed when the integuments are carefully removed. In anatropal seeds the raphe forms a distinct ridge along one side of the seed (fig. 41).

The position of the seed as regards the pericarp resembles that of the ovule in the ovary, and the same terms are applied--erect, ascending, pendulous, suspended, curved, &c. These terms have no reference to the mode in which the fruit is attached to the axis. Thus the seed may be erect while the fruit itself is pendent, in the ordinary meaning of that term. The part of the seed next the axis or the ventral suture is its face, the opposite side being the back. Seeds exhibit great varieties of form. They may be flattened laterally (_compressed_), or from above downwards (_depressed_). They may be round, oval, triangular, polygonal, rolled up like a snail, as in _Physostemon_, or coiled up like a snake, as in _Ophiocaryon paradoxum_.

[Illustration:

FIG. 37.--Seed of Pine (_Pinus_), with a membranous appendage w to the testa, called a wing.

FIG. 38.--Young anatropal seed of the white Water-lily (_Nymphaea alba_), cut vertically. It is attached to the placenta by the funicle f, cellular prolongations from which form an aril a a. The vessels of the cord are prolonged to the base of the nucellus n by means of the raphe r. The base of the nucellus is indicated by the chalaza ch, while the apex is at the micropyle m. The covering of the seed is marked i. n is the nucellus or perisperm, enclosing the embryo-sac es, in which the endosperm is formed. The embryo e, with its suspensor, is contained in the sac, the radicle pointing to the micropyle m.

FIG. 39.--Arillode a, or false aril, of the Spindle-tree (_Euonymus_), arising from the micropyle f.

FIG. 40.--Anatropal seed of the Orange (_Citrus Aurantium_) opened to show the chalaza c, which forms a brown spot at one end.

FIG. 41.--Entire anatropal seed of the Orange (_Citrus Aurantium_), with its rugose or wrinkled testa, and the raphe r ramifying in the thickness of the testa on one side.]

The endosperm formed in the embryo-sac of angiosperms after fertilization, and found previous to it in gymnosperms, consists of cells containing nitrogenous and starchy or fatty matter, destined for the nutriment of the embryo. It occupies the whole cavity of the embryo-sac, or is formed only at certain portions of it, at the apex, as in _Rhinanthus_, at the base, as in _Vaccinium_, or in the middle, as in _Veronica_. As the endosperm increases in size along with the embryo-sac and the embryo, the substance of the original nucellus of the ovule is gradually absorbed. Sometimes, however, as in Musaceae, Cannaceae, Zingiberaceae, no endosperm is formed; the cells of the original nucellus, becoming filled with food-materials for the embryo, are not absorbed, but remain surrounding the embryo-sac with the embryo, and constitute the _perisperm_. Again, in other plants, as Nymphaeaceae (fig. 38) and Piperaceae, both endosperm and perisperm are present. It was from observations on cases such as these that old authors, imagining a resemblance betwixt the plant-ovule and the animal ovum, applied the name _albumen_ to the outer nutrient mass or perisperm, and designated the endosperm as _vitellus_. The term albumen is very generally used as including all the nutrient matter stored up in the seed, but it would be advisable to discard the name as implying a definite chemical substance. There is a large class of plants in which although at first after fertilization a mass of endosperm is formed, yet, as the embryo increases in size, the nutrient matter from the endospermic cells passes out from them, and is absorbed by the cells of the embryo plant. In the mature seed, in such cases, there is no separate mass of tissue containing nutrient food-material apart from the embryo itself. Such a seed is said to be _exalbuminous_, as in Compositae, Cruciferae and most Leguminosae (e.g. pea, fig. 35). When either endosperm or perisperm or both are present the seed is said to be _albuminous_.

[Illustration: FIG. 42.--The dicotyledonous embryo of the Pea laid open. c, c, The two fleshy cotyledons, or seed-lobes, which remain under ground when the plant sprouts; r, the radicular extremity of the axis whence the root arises; t, the axis (hypocotyl) bearing the young stalk and leaves g (plumule), which lie in a depression of the cotyledons f.]

The albumen varies much in its nature and consistence, and furnishes important characters. It may be farinaceous or mealy, consisting chiefly of cells filled with starch, as in cereal grains, where it is abundant; fleshy or cartilaginous, consisting of thicker cells which are still soft, as in the coco-nut, and which sometimes contain oil, as in the oily albumen of _Croton_, _Ricinus_ and poppy; horny, when the cell-walls are slightly thickened and capable of distension, as in date and coffee; the cell-walls sometimes become greatly thickened, filling up the testa as a hard mass, as in vegetable ivory (_Phytelephas_). The albumen may be uniform throughout, or it may present a mottled appearance, as in the nutmeg, the seeds of Anonaceae and some Palms, where it is called _ruminated_. This mottled appearance is due to a protrusion of a dark lamella of the integument between folded protuberances of albumen. A cavity is sometimes left in the centre which is usually filled with fluid, as in the coco-nut. The relative size of the embryo and of the endosperm varies much. In Monocotyledons the embryo is usually small, and the endosperm large, and the same is true in the case of coffee and many other plants amongst Dicotyledons. The opposite is the case in other plants, as in the Labiatae, Plumbaginaceae, &c.

The embryo consists of an axis bearing the _cotyledons_ (fig. 42, c), or the first leaves of the plant. To that part of this axis immediately beneath the cotyledons the terms _hypocotyl_, _caulicle_ or _tigellum_ (t) have been applied, and continuous backwards with it is the young root or _radicle_ (r), the descending axis, their point of union being the collar or neck. The terminal growing bud of the axis is called the _plumule_ or _gemmule_ (g), and represents the ascending axis. The radicular extremity points towards the micropyle, while the cotyledonary extremity is pointed towards the base of the ovule or the chalaza. Hence, by ascertaining the position of the micropyle and chalaza, the two extremities of the embryo can in general be discovered. It is in many cases difficult to recognize the parts in an embryo; thus in _Cuscuta_, the embryo appears as an elongated axis without divisions; and in _Caryocar_ the mass of the embryo is made up by the radicular extremity and hypocotyl, in a groove of which the cotyledonary extremity lies embedded (fig. 52). In some monocotyledonous embryos, as in Orchidaceae, the embryo is a cellular mass showing no parts. In parasitic plants also which form no chlorophyll, as _Orobanche_, _Monotropa_, &c., the embryo remains without differentiation, consisting merely of a mass of cells until the ripening of the seed. When the embryo is surrounded by the endosperm on all sides except its radicular extremity it is internal (see figs. 19, 20); when lying outside the endosperm, and only coming into contact with it at certain points, it is external, as in grasses (e.g. wheat, fig. 22). When the embryo follows the direction of the axis of the seed, it is axile or axial (fig. 43); when it is not in the direction of the axis, it becomes abaxile or abaxial. In campylotropal seeds the embryo is curved, and in place of being embedded in endosperm, is frequently external to it, following the concavity of the seed (fig. 44), and becoming peripherical, with the chalaza situated in the curvature of the embryo, as in Caryophyllaceae.

It has been already stated that the radicle of the embryo is directed to the micropyle, and the cotyledons to the chalaza. In some cases, by the growth of the integuments, the former is turned round so as not to correspond with the apex of the nucellus, and then the embryo has the radicle directed to one side, and is called excentric, as is seen in Primulaceae, Plantaginaceae and many palms, especially the date. The position of the embryo in different kinds of seeds varies. In an orthotropal seed the embryo is inverted or _antitropal_, the radicle pointing to the apex of the seed, or to the part opposite the hilum. Again, in an anatropal seed the embryo is erect or _homotropal_ (fig. 43), the radicle being directed to the base of the seed. In curved or campylotropal seeds the embryo is folded so that its radicular and cotyledonary extremities are approximated, and it becomes _amphitropal_ (fig. 44). In this instance the seed may be exalbuminous, and the embryo may be folded on itself; or albuminous, the embryo surrounding more or less completely the endosperm and being peripherical. According to the mode in which the seed is attached to the pericarp, the radicle may be directed upwards or downwards, or laterally, as regards the ovary. In an orthotropal seed attached to the base of the pericarp it is superior, as also in a suspended anatropal seed. In other anatropal seeds the radicle is inferior. When the seed is horizontal as regards the pericarp, the radicle is either centrifugal, when it points to the outer wall of the ovary; or centripetal, when it points to the axis or inner wall of the ovary. These characters are of value for purposes of classification, as they are often constant in large groups of genera.

Plants in which there are two cotyledons produced in the embryo are _dicotyledonous_. The two cotyledons thus formed are opposite to each other (figs. 42 and 45), but are not always of the same size. Thus, in Abronia and other members of the order Nyctaginaceae, one of them is smaller than the other (often very small), and in _Carapa guianensis_ there appears to be only one, in consequence of the intimate union which takes place between the two. The union between the cotyledonary leaves may continue after the young plant begins to germinate. Such embryos have been called _pseudomonocotyledonous_. The texture of the cotyledons varies. They may be thick, as in the pea (fig. 42), exhibiting no traces of venation, with their flat internal surfaces in contact, and their backs more or less convex; or they may be in the form of thin and delicate laminae, flattened on both sides, and having distinct venation, as in _Ricinus_, _Jatropha_, _Euonymus_, &c. The cotyledons usually form the greater part of the mature embryo, and this is remarkably well seen in such exalbuminous seeds as the bean and pea.

[Illustration:

FIG. 43.--Seed of Pansy (_Viola tricolor_) cut vertically. The embryo pl is axial, in the midst of fleshy endosperm al. The seed is anatropal, and the embryo is homotropal; the cotyledons co point to the base of the nucellus or chalaza ch, while the radicle, or the other extremity of the embryo, points to the micropyle, close to the hilum h. The hilum or base of the seed, and the chalaza or base of the nucellus are united by means of the raphe r.

FIG. 44.--Seed of the Red Campion (_Lychnis_), cut vertically, showing the peripheral embryo, with its two cotyledons and its radicle. The embryo is curved round the albumen, so that its cotyledons and radicle both come near the hilum (_amphitropal_).

FIG. 45.--Mature dicotyledonous embryo of the Almond, with one of the cotyledons removed. r, Radicle; t, young stem or caulicle; c, one of the cotyledons left; i, line of insertion of the cotyledon which has been removed; g, plumule.

FIG. 46.--Exalbuminous seed of Wallflower (Cheiranthus) cut vertically. The radicle r is folded on the edges of the cotyledons c which are accumbent.

FIG. 47.--Transverse section of the seed of the Wallflower (_Cheiranthus_), showing the radicle r folded on the edges of the accumbent cotyledons c.

FIG. 48.--Transverse section of the seed of the Dame's Violet (_Hesperis_). The radicle r is folded on the back of the cotyledons c, which are said to be incumbent.]

Cotyledons are usually entire and sessile. But they occasionally become lobed, as in the walnut and the lime; or petiolate, as in _Geranium molle_; or auriculate, as in the ash. Like leaves in the bud, cotyledons may be either applied directly to each other, or may be folded in various ways. In geranium the cotyledons are twisted and doubled; in convolvulus they are corrugated; and in the potato and in _Bunias_, they are spiral,--the same terms being applied as to the foliage leaves. The radicle and cotyledons are either straight or variously curved. Thus, in some cruciferous plants, as the wallflower, the cotyledons are applied by their faces, and the radicle (figs. 46, 47) is folded on their edges, so as to be lateral; the cotyledons are here _accumbent_. In others, as _Hesperis_, the cotyledons (fig. 48) are applied to each other by their faces, and the radicle, r, is folded on their back, so as to be dorsal, and the cotyledons are _incumbent_. Again, the cotyledons are _conduplicate_ when the radicle is dorsal, and enclosed between their folds. In other divisions the radicle is folded in a spiral manner, and the cotyledons follow the same course.

In many gymnosperms more than two cotyledons are present, and they are arranged in a whorl. This occurs in Coniferae, especially in the pine, fir (fig. 49), spruce and larch, in which six, nine, twelve and even fifteen have been observed. They are linear, and resemble in their form and mode of development the clustered or fasciculated leaves of the larch. Plants having numerous cotyledons are termed _polycotyledonous_. In species of _Streptocarpus_ the cotyledons are permanent, and act the part of leaves. One of them is frequently largely developed, while the other is small or abortive.

[Illustration:

FIG. 49.--Polycotylodonous embryo of the Pine (_Pinus_) beginning to sprout. t, Hypocotyl; r, radicle. The cotyledons c are numerous. Within the cotyledons the primordial leaves are seen, constituting the plumule or first bud of the plant.

FIG. 50.--Embryo of a species of Arrow-grass (_Triglochin_), showing a uniform conical mass, with a slit s near the lower part. The cotyledon c envelops the young bud, which protrudes at the slit during germination. The radicle is developed from the lower part of the axis r.

FIG. 51.--Grain of wheat (_Triticum_) germinating, showing (b) the cotyledon and (c) the rootlets surrounded by their sheaths (_coleorrhizae_).

FIG. 52.--Embryo of _Caryocar_. t, Thick hypocotyl, forming nearly the whole mass, becoming narrowed and curved at its extremity, and applied to the groove s. In the figure this narrowed portion is slightly separated from the groove; c, two rudimentary cotyledons.]

In those plants in which there is only a single cotyledon in the embryo, hence called _monocotyledonous_, the embryo usually has a cylindrical form more or less rounded at the extremities, or elongated and fusiform, often oblique. The axis is usually very short compared with the cotyledon, which in general encloses the plumule by its lower portion, and exhibits on one side a small slit which indicates the union of the edges of the vaginal or sheathing portion of the leaf (fig. 50). In grasses, by the enlargement of the embryo in a

## particular direction, the endosperm is pushed on one side, and thus

the embryo comes to lie outside at the base of the endosperm (figs. 22, 51). The lamina of the cotyledon is not developed. Upon the side of the embryo next the endosperm and enveloping it is a large shield-shaped body, termed the _scutellum_. This is an outgrowth from the base of the cotyledon, enveloping more or less the cotyledon and plumule, in some cases, as in maize, completely investing it; in other cases, as in rice, merely sending small prolongations over its anterior face at the apex. By others this scutellum is considered as the true cotyledon, and the sheathing structure covering the plumule is regarded as a ligule or axillary stipule (see GRASSES). In many aquatic monocotyledons (e.g. _Potamogeton_, _Ruppia_ and others) there is a much-developed hypocotyl, which forms the greater part of the embryo and acts as a store of nutriment in germination; these are known as _macropodous_ embryos. A similar case is that of _Caryocar_ among Dicotyledons, where the swollen hypocotyl occupies most of the embryo (fig. 52). In some grasses, as oats and rice, a projection of cellular tissue is seen upon the side of the embryo opposite to the scutellum, that is, on the anterior side. This has been termed the _epiblast_. It is very large in rice. This by some was considered the rudimentary second cotyledon; but is now generally regarded as an outgrowth of the sheath of the true cotyledon. (A. B. R.)

FRUIT AND FLOWER FARMING. The different sorts of fruits and flowers are dealt with in articles under their own headings, to which reference may be made; and these give the substantial facts as to their cultivation. See also the article HORTICULTURE.

TABLE I.--_Extent of Orchards in Great Britain in each Year, 1887 to 1901._

+------+---------++------+---------++------+---------+ | Year.| Acres. || Year.| Acres. || Year.| Acres. | +------+---------++------+---------++------+---------+ | 1887 | 202,234 || 1892 | 208,950 || 1897 | 224,116 | | 1888 | 199,178 || 1893 | 211,664 || 1898 | 226,059 | | 1889 | 199,897 || 1894 | 214,187 || 1899 | 228,603 | | 1890 | 202,305 || 1895 | 218,428 || 1900 | 232,129 | | 1891 | 209,996 || 1896 | 221,254 || 1901 | 234,660 | +------+---------++------+---------++------+---------+

TABLE II.--_Areas under Orchards in England, Wales and Scotland--Acres._

+------+----------+--------+---------+--------------+ | Year.| England. | Wales. |Scotland.|Great Britain.| +------+----------+--------+---------+--------------+ | 1896 | 215,642 | 3677 | 1935 | 221,254 | | 1897 | 218,261 | 3707 | 2148 | 224,116 | | 1898 | 220,220 | 3690 | 2149 | 226,059 | | 1899 | 222,712 | 3666 | 2225 | 228,603 | | 1900 | 226,164 | 3695 | 2270 | 232,129 | | 1901 | 228,580 | 3767 | 2313 | 234,660 | | 1908 | 244,430 | 3577 | 2290 | 250,297 | +------+----------+--------+---------+--------------+

GREAT BRITAIN

The extent of the fruit industry may be gathered from the figures for the acreage of land under cultivation in orchards and small fruit plantations. The Board of Agriculture returns concerning the orchard areas of Great Britain showed a continuous expansion year by year from 199,178 acres in 1888 to 234,660 acres in 1901, as will be learnt from Table I. There was, it is true, an exception in 1892, but the decline in that year is explained by the circumstance that since 1891 the agricultural returns have been collected only from holdings of more than one acre, whereas they were previously obtained from all holdings of a quarter of an acre or more. As there are many holdings of less than an acre in extent upon which fruit is grown, and as fruit is largely raised also in suburban and other gardens which do not come into the returns, it may be taken for granted that the actual extent of land devoted to fruit culture exceeds that which is indicated by the official figures. In the Board of Agriculture returns up to June 1908, 308,000 acres are stated to be devoted to fruit cultivation of all kinds in Great Britain. Table II. shows that the expansion of the orchard area of Great Britain is mainly confined to England, for it has slightly decreased in Wales and Scotland. The acreage officially returned as under orchards is that of arable or grass land which is also used for fruit trees of any kind. Conditions of soil and climate determine the irregular distribution of orchards in Great Britain. The dozen counties which possess the largest extent of orchard land all lie in the south or west of the island. According to the returns for 1908 (excluding small fruit areas) they were the following:--

+----------+--------++-----------+--------++----------+------+ | County. | Acres. || County. | Acres. || County. |Acres.| +----------+--------++-----------+--------++----------+------+ | Kent | 32,751 || Worcester | 23,653 || Salop | 4685 | | Devon | 27,200 || Gloucester| 20,424 || Dorset | 4464 | | Hereford | 28,316 || Cornwall | 5,415 || Monmouth | 3914 | | Somerset | 25,279 || Middlesex | 5,300 || Wilts | 3630 | +----------+--------++-----------+--------++----------+------+