A handbook of systematic botany

Order 2. Corylaceæ (Hazel-nuts). Monœcious. The ♂-catkins are long and cylindrical; the ♂-flowers are placed singly in the axil of the subtending-leaf (cover-scale); they are naked and formed of a number of divided stamens, which are partly united with the cover-scale, 4 in the Hazel, apparently 8 (Figs. 330 A, 329 B, C), more on the Hornbeam. The ♀-flowers have a very small, superior perianth; in the axil of each cover-scale a 2-flowered dichasium (Fig. 329 D) is present, of which the central flower (* in Fig. 330 B) is suppressed. The gynœceum is bicarpellary as in the Birches; the ovary is bilocular, with two long styles (Fig. 329 D-F); the loculi have 1 (-2) ovules (Fig. 330 B). Each single ♀-flower and fruit is surrounded by a leaf-like covering, the cupule (husk), which is formed of three floral-leaves (namely, the bract of a lateral flower, and its own bracteoles; thus in Fig. 330 B, α, α′, β’ form the cupule for the left-hand flower, and β, α₁, β₁, the cupule for the right-hand).

Corylus (Hazel-nut, Fig. 329). The long, cylindrical ♂-catkins pass the winter naked, 2–3 together, on short branches. The very small ♀-catkins are enclosed in buds, in which they pass the winter; these buds are situated in the axils of the fallen foliage-leaves, and it is only by their larger size that they may be distinguished from the ordinary foliage-buds. In spring the ♀-catkins are easily recognised by their red, projecting stigmas (Fig. 329 A). The cupule—the “husk”—is tubular, fringed, and envelopes the nut. The leaves are alternate and unsymmetrical, the external side being larger than the internal; this is connected with the vernation, the blade being conduplicate in the bud; the stipules are deciduous. The bud-scales are formed of stipules, the most internal having a leaf-blade attached to them which is suppressed in the external ones. The cotyledons remain underground on germination.

Carpinus (C. betulus, Hornbeam). The ♂-and ♀-catkins do not appear till the leaves are shooting. The ♀-catkin in this instance is also long and cylindrical. The cupule in C. betulus is 3-lobed, and to a slight extent only embraces the base of the ribbed nut (Fig. 331); each lobe corresponds to a floral-leaf. Whilst the carpels are placed medianly in Corylus, in Carpinus, on the other hand, they are situated transversely, as in the case of the Betulaceæ. The lamina of the leaf is not conduplicate in the bud, but flat, and folded only along the lateral veins, which are also indicated in the form of the fully-developed leaf; otherwise the vegetative characters are essentially the same as in the Hazel. The cotyledons are aerial.—Ostrya resembles the Hornbeam, but the cupule completely envelopes the nut, as a sac open at the apex (Eur., N. Am., Japan).

Order 3. Cupuliferæ. Monœcious. The inflorescences make their appearance with the leaves, arising in the axils of the leaves of the same year. A woody cupule furnished externally with scales or spines is common, and surrounds 1-several flowers (the cupule in the Corylaceæ never encloses more than a single flower or fruit). The ♂-flower has a united perianth, which is, however, 4–6 partite, and encloses an indefinite number of undivided stamens. The ♀-flower has a superior, 6-merous perianth (3 + 3, compare Figs. 332 D, 334); the gynœceum is formed of 3 (or in Castanea 4–6) carpels with a corresponding number of stigmas (Figs. 332 D, H; 334, 335); and the ovary has at the base 3 (-6) loculi (Fig. 333), each of which has 2 pendulous anatropous ovules; the fruit is a one-seeded nut (Figs. 332 H, 336).

The cupule of the Cupuliferæ, according to the opinion of Eichler, is formed by united bracteoles, (compare Fig. 333, where the four valves in the cupule of Castanea are considered as bracteoles of the lateral flowers of the dichasium); according to another view (see Prantl, in Engler’s Bot. Jahrb., viii., 1889), it is a ring-like axial outgrowth independent of the bracteoles of the flower, whose scales and spines are floral-leaves. The cupule in the Oak only encloses the base of the fruit, but in the Eating-chestnut and Beech the fruit is completely enclosed, and consequently the cupule must divide into a number of valves (generally 4) to allow the fruit to escape. In the 3-flowered dichasia of Pasania, Sect. Eupasania (Trop. Ind.), each individual flower has its own cupule of the same structure and development as in Quercus; and, moreover, each group of flowers has externally the typical six bracteoles.

Castanea (Eating-chestnut, Fig. 332). The catkins are erect (A), cylindrical, with the ♀ at the base and the ♂ at the top, or some are entirely ♂ and composed of small dichasia. The cupule (C, F) is 4-valved, provided with spines, and entirely envelops the 3 nuts; it is already developed at the time of flowering.—♂-flowers are most frequently borne in 7-flowered dichasia, and have a well developed perianth, most frequently consisting of 6 leaves in two whorls (Fig. 332 B), and a large number of stamens. ♀-flowers are most frequently borne in 3-flowered dichasia (Figs. 332 C, 333); the letters in Fig. 333 indicate the older theory, according to which the 4 bracteoles (α′-β′) of the two lateral flowers are thick and united into a single 4-valved, woody cupule, which surrounds the 3 nuts, and is furnished externally with spines; the spines are well developed hair-structures.—6 carpels in two whorls.—The leaves in the vertical shoots have a divergence of 2/5, 3/8, 5/13; on the horizontal shoots they are alternate. The cotyledons remain underground on germination.

Fagus (Beech). The ♂-catkins are pendulous, capitate; the ♂-flowers have an obliquely bell-shaped, fringed perianth, with 6–20 stamens. ♀-catkins erect, 2-flowered, borne singly in the axil of foliage-leaves of the same year; the ♀-flower has a gynœceum formed of 3 carpels, bearing an epigynous, 6-leaved perianth (Fig. 334). In this genus the dichasium has only 2 flowers, the central one being suppressed. The cupule contains, therefore, only 2 triangular nuts (“mast”). All the shoots have the leaves arranged in two rows; the rows are on the underside, being only about 90° distant from each other; the buds on the other hand approach each other towards the upper side. The bud-scales are stipules without laminæ; in vernation the laminæ are folded along the lateral ribs, the upper lateral portion being the largest (as in Hornbeam and Chestnut). The cotyledons are folded, and at germination are aerial, large, and reniform. 4 species (Europe, Japan, N. Am.)—Nothofagus (S. Am., New Zealand, S. Austr.)

Quercus (Oak, Fig. 335). Catkins simple. ♂-catkins long, thin, pendulous, few-flowered. ♀-catkins erect; the cupule is cup-like, entire, and encloses only the base of the solitary nut (“acorn”).—The ♂-flower has a similar construction to that of the Chestnut. The ♀-catkin has not more than 5 flowers (single-flowered dichasia, in which only the central flower is developed). The scales on the cupules are no doubt leaf-structures in this case also. According to another theory, the scales are hair-structures; they arise on the internal face of the young cupule apparently in descending, but really in ascending order. The rim of the cupule gradually expands. In the ♀-flower (Fig. 335) the loculi of the gynœceum, together with the ovules, are not developed until after pollination.—The leaves in all cases have a divergence of 2/5; the lowermost leaves on the shoots are reduced to stipules which serve as the bud-scales (5 rows). The laminæ are conduplicate, as in Corylus, and the external side is the broadest. The cotyledons are fleshy and remain underground. 200 species.—Pasania (100 species).

368 species, in temperate climates, especially in Europe and N. America. Authenticated forests have been found in the Oligocene. The Beech has one species, Fagus sylvatica, in Europe; it is a most important forest tree (in Denmark the most important) and reaches its most northern limit near Alvesund in Norway (60° N.L.), its northern boundary line passing from Alvesund in a zig-zag line through Ludwigsort, south of Königsberg, in Prussia, towards the Crimea. According to Steenstrup and Vaupell, the Beech did not make its appearance in Denmark until a comparatively recent time, the Oak then being partially supplanted. Other species of Beech are found in N. America and Japan. Several species of Nothofagus occur in the South West of S. America, and in the colder regions of the southern hemisphere. The Oaks grow especially in temperate regions, e.g. in Western Asia, N. America, and the mountains of Mexico. Evergreen species are found in Tropical Asia, Himalaya, Japan and the Mediterranean region. In this country there is one species of Oak (Q. robur), of which there are three varieties (Q. pedunculata, intermedia, sessiliflora). The Eating-chestnut is found in the South of Europe, but is cultivated in the midland and southern counties of England.—Uses. The wood of these trees is very useful as timber. The wood of Q. tinctoria has a yellow colouring matter (Quercitron-wood). The bark of the Oak contains a large quantity of tannic acid, and is used for tanning; for this purpose also the cupules of Q. vallonea, ægilops, græca, and others from the Eastern Mediterranean, are used under the name of “Valloons.” The Cork-oak (Q. suber; S.W. Europe) is the most important tree from which cork is obtained,

its bark being very largely developed and stripped for cork. Gall-nuts are found on many species; those of Q. lusitanica, var. infectoria (Eastern Mediterranean) are officinal, and likewise the fruits (acorns) and the bark of Quercus pedunculata and sessiliflora. Oil is obtained from the Beech “mast.” The nuts of the Chestnut tree are edible.

Family 4. Juglandifloræ.

This family resembles the Quercifloræ in the catkin-like inflorescences, the imperfect, unisexual flowers, the epigynous perianth and the woody shoots with scattered leaves, etc., though it is in other respects very dissimilar; one point of difference is the presence of aromatic compounds, but a more important divergence is found in the structure of the gynœceum, which is formed of two carpels with one loculus and has one basal, orthotropous and erect ovule, which, as in the Quercifloræ, does not become developed until after pollination; the fruit too is very different, being generally a drupe. Endosperm absent.

Order 1. Juglandaceæ (Walnuts). Leaves scattered, imparipinnate, rich in aromatic compounds. Stipules absent. Flowers unisexual. Monœcious. The ♂-catkins are lateral, generally on naked branches of the previous year, cylindrical, pendulous, many-flowered; the two bracteoles and the 2–4-leaved perianth of the ♂-flower unite with the subtending bract; the ♂-flower has indefinite stamens (6–20 in Juglans, Fig. 337 A-D). The ♀-catkins are terminal, generally on branches of the same year, few-flowered (Fig. 337 F); the ♀-flowers have a superior, 4-leaved perianth, a bicarpellate gynœceum, two styles with stigmas on the internal surface. The ovary, bracteoles and bract all unite together (Fig. 337 E). The fruit is generally a green or black drupe,[34] whose flesh (outer soft portion) in Carya and Juglans ruptures more or less irregularly, and frees the stone (“Walnut”).—The stone in Juglans is divided internally by one true (Fig. 337 H) and by several false, low partition walls into several incomplete compartments, so that the two large cotyledons become lobed and incised to fit like a cast into the irregularities of the inner surface of the stone; the embryo is exendospermous and covered with a thin testa.—The leaf scars are large and cordate with 3 groups of vascular bundles. The PITH in Juglans and Pterocarya is divided into chambers. The stone ruptures, on germination, along the dorsal suture into 2 valves; the cotyledons remain underground. In Juglans regia a long row of accessory buds is found on the lowest internode (epicotyl) above the axils of the cotyledons. Pollination by the wind. Both protogynous and protandrous examples of Juglans regia occur.—33 species, mostly in temperate North America.—Uses. Walnuts are obtained from J. nigra and regia; Hickory from North American species of Carya. The oil-containing seeds of several species are edible. Pterocarya and others are cultivated as ornamental plants.

Order 2. Myricaceæ. To this order belong shrubs or trees which have penninerved, simple, at most lobed or pinnatifid leaves, with or without stipules, and with yellow, aromatic, resin glands (Fig. 338 a). The flowers, situated in catkin-like spikes, are unisexual and naked, and supported by scale-like floral-leaves. ♂-flower: 4–6 (–16) stamens with short filaments; ♀: generally situated singly. The gynœceum has a short style with 2 long stigmas, and unites with the bracteoles, which form wing-like outgrowths on the ripe drupe as in Pterocarya in the Juglandaceæ (Fig. 338). Cotyledons fleshy (Fig. 338 b).—Myrica; Comptonia.

Family 5. Urticifloræ.

The flowers are regular, hypogynous, nearly always unisexual, small and insignificant, with single, green perianth of 4–5 leaves. Stamens 4–5, placed opposite the leaves of the perianth. Ovary formed of 1 or 2 carpels, most frequently unilocular, with one ovule (Fig. 340). The fruit is a nut, more rarely a drupe, with one seed, generally endospermous. The Nettles are the sole order in the family which has only one carpel (1 stigma); this turns the posterior side to the front (Fig. 340). The others have two carpels (2 stigmas) but the anterior only is fertile (Fig. 346) except in a few Ulmaceæ and Moraceæ.

The majority are trees or shrubs with petiolated leaves, stipulate; rough hairs are very frequently developed upon the leaves. The flowers are very often crowded together in the inflorescence, which is rarely catkin-like. Peculiar aggregations of fruits are found in some orders. Latex and tough bast, which is used technically, are also frequently found. Cystoliths are found in the epidermis of many species of Ficus, Urtica, and others. Wind- or self-pollination is most common, as in the Quercifloræ and Juglandifloræ. In the Urticaceæ, Morus and some others, the stamens lie incurved in the bud, and when ripe straighten themselves suddenly and elastically, and thus small clouds of pollen-grains are ejected with considerable violence on to the stigmas, which are often provided with brush-like hairs (Fig. 341). The formation of honey does not take place.

Order 1. Ulmaceæ (Elms).—Trees or shrubs without latex. Leaves simple, arranged in two rows (divergence 1/2), oblique (the inner side, nearer the axis, being the larger), strongly penninerved, dentate, hispid; stipules deciduous. In opposition to the other Nettle-like plants the flowers are often ☿ with a united cup- or saucer-like, generally 4–(5)–6-divided perianth, and a corresponding or larger number of opposite erect stamens. The gynœceum has two carpels (2 stigmas), generally one loculus with one pendulous, anatropous or amphitropous ovule,[35] seldom two loculi and 2 ovules. Fruit one-seeded (nut or drupe). Embryo without endosperm.

A. Ulmeæ. The fruit is a winged nut (Fig. 339), the embryo straight, without endosperm. Anthers extrorse.—Ulmus (Elm). The flowers are situated in inflorescences which develop from the lower buds of the shoot of the preceding year. The lowermost bud-scales are empty, the uppermost support either solitary flowers, or small, dichasial or unipared scorpioid inflorescences. The terminal bud on the vegetative shoot quickly falls off, and the upper lateral bud continues the growth sympodially. Flowering takes place before the leaf-buds open. The flowers are wind-pollinated and have no honey. Fossil species have been found in the Oligocene.

Order 2. Urticaceæ (Nettles).—The majority of species are herbs with simple, stipulate leaves; they have no latex; stinging hairs abundant. The flowers (Fig. 340) are unisexual, generally 2-merous and arranged in clusters, which are united into catkin-like inflorescences. The perianth is composed very often of 4 (2 + 2) free, or in the ♀-flowers generally united, green leaves; the 4 (2 + 2) stamens are opposite the perianth-leaves, the filaments are bent inwards in the bud and throw themselves elastically towards the outside. The gynœceum has one style and one stigma (capitate or brush-like, Fig. 341); the ovary is unilocular, with one orthotropous, erect ovule (all other orders of this family have inverted or curved ovules). Fruit, a nut or drupe. Endosperm present (in Urtica very little), oily. Embryo straight. The STINGING HAIRS are club-shaped, very turgid, and provided with a siliceous, brittle apex, which breaks off in an oblique direction and allows the poisonous cell-sap to be forced out. In many tropical Nettles this is so strong that it may produce partial paralysis. There is no rudiment of an ovary in the ♂-flowers (Fig. 340 A). The PERIANTH in the ♀-flower differs from that of the ♂ in having the two internal leaves generally much larger and enveloping the fruit (Fig. 340 B); it often happens that all the perianth-leaves are united to form a gamophyllous envelope. ☿-flowers may occur among the others.—The inflorescences among our native species are dichasia, which become transformed into unilateral scorpioid cymes by the development of the bud of the 2nd bracteole. In Parietaria they are more pressed together, and the floral-leaves at the same time are also raised on their axillary shoots to just beneath the flower. As a rule, not only in this order but also in those related to it, a small vegetative branch is situated in the axil of the foliage-leaf, and this bears an inflorescence on each side at its base.

Urtica (Nettle) has opposite leaves with distinct stipules and stinging hairs. The perianth-leaves of the ♀-flower are free (Fig. 340).—Parietaria (Pellitory) has scattered leaves without large stipules, and stinging hairs are absent. The ♀-perianth is 4-toothed, flask- or bell-shaped.—Pilea is a tropical genus with trimerous, zygomorphic ♀-flowers, the posterior perianth-leaf being much larger than the two others, and more or less hood shaped.—The flower of Forskohlea is the most reduced; the ♂-flower has only one stamen, and the ♀-as well as the ♂-flowers have a one-sided, tongue like perianth (?). Pouzolzia.

Order 3. Moraceæ (Mulberries). Nearly all trees or shrubs, seldom herbs, generally with latex. The leaves are scattered, and not infrequently lobed. The flowers are unisexual (monœcious or diœcious) and arranged in catkin- or capitulum-like, compound inflorescences. Perianth-leaves 2–6, generally 4, with an equal number of stamens opposite to them, as in the Nettles. The ovary is 1–seldom 2-locular, and has 2 stigmas (it is thus formed from 2 carpels) seldom only one style with one stigma. One ovule in each loculus, more or less curved, and pendulous; micropyle directed upwards. Fruit usually a drupe. The embryo is generally curved inside the fleshy endosperm, or it is exendospermous.

A. Moreæ. The filaments are incurved in the bud. Leaves folded in the bud—Morus (Mulberry) (Figs. 342–344). Monœcious. The inflorescences are catkin-like in appearance, but in reality composed of many small dichasia. The flowers are similar to those of the Nettle, but with 2 carpels: in the ♂ with perianth 2 + 2, and stamens 2 + 2 (Fig. 342), in the ♀, perianth 2 + 2, and 2 carpels in regular alternation. The small drupes are enveloped by the perianth, which eventually becomes fleshy, and as all the flowers on the axis very accurately fit together, the collection of fruits is formed, which we call a Mulberry (Fig. 344). The leaves are folded in the buds, and have small stipules. The following are allied to Morus:—Maclura, Broussonetia (the Paper-mulberry tree) which has spheroid ♀ inflorescences (made up of dichasia), etc.

B. Artocarpeæ. Filaments straight in the bud; foliage-leaves with convolute vernation. An interpetiolar leaf-sheath (ocrea) formed in the axil of each leaf by the connate stipules, covers the younger leaves as a hood. It falls off as the leaf expands, and leaves a ring-like scar on the stem.—Ficus (the Fig). The inflorescence (the so-called syconus) has a pear-shaped, fleshy, but hollow axis, on the interior surface of which the flowers are situated (Fig. 345). It is a kind of capitulum, with a hollow receptacle, whose “involucral” leaves close over the entrance to the interior; it is not, however, a simple capitulum, but a coalescence of cymose inflorescences. The edible parts are the fleshy stem-portion and perianth-leaves. The ♂-flower has a 2–6 divided perianth, 1–2 (–6) stamens; the ♀-flower has an oblique ovary. The fruits are drupes, with thin flesh.—Many species have aerial roots, and some live as epiphytes on trees. Pollination, in the edible Fig, is effected by a small Gall-wasp (Cynips psenes L.), which lays its eggs in the Fig, and hence carries the pollen away. Even in very ancient times it was customary to hang infected wild Figs on the branches of cultivated ones, so that the young Gall-wasps, as they emerged, could immediately effect the pollination (caprification). Ficus carica, and other species, have two kinds of ♀-flowers, besides the ♂-flowers. One kind has a short style and no stigmatic hairs, and it is only in the ovaries of these that the wasps lay their eggs (gall-flowers); the other kind has a long style and well-developed stigmatic-hairs, but the wasps cannot reach their ovaries—these are “seed-flowers.” There are, moreover, two kinds of plants of Ficus carica; ♀-plants, which have only seed-flowers, and bear the edible Figs, and ♂-plants (called “Caprificus”), which bear inedible fruits, and have ♂-flowers at the upper part of the Fig, but gall-flowers at the base. [The Caprificus, at Naples, bears three crops of inedible Figs each year, viz. Mamme (April), Profichi (June), Mamnoni (August). The ♂-flowers are produced especially in June, the first Figs being almost entirely ♀, and the last having but few ♂-flowers. Each crop produces a new generation of Fig-wasps. The female wasp enters the Figs on the Caprificus, and lays one egg in each flower, with the result that the flower developes into a kind of gall. The mother-wasp dies within the Fig. The male wasp is wingless; it bites a small passage into the ovaries containing the female wasps, and impregnates them; the female wasps then escape from the Fig, those in the Profichi carrying pollen away with them as they pass out. They then enter another Fig, lay their eggs, and die. The edible Fig-tree similarly has three crops in the year, Fiori di fico, Pedagnuoli, Cimaruoli. The wasps, entering these Figs, are unable to lay their eggs in the ovary, but, nevertheless, they effect cross-pollination on entering the Pedagnuoli, which bear fertile seeds.]

Order 4. Cannabaceæ. The plants which belong to this order are aromatic herbs, either annuals or perennials, without latex. Leaves palminerved, and more or less divided, hispid, and with free, persistent stipules. Flowers always diœcious; ♂-flowers in panicles, formed of dichasia, passing over into uniparous scorpioid cymes. They differ from the Nettles, particularly in the 5-leaved perianth of the ♂-flower, the 5 stamens (Fig. 346–351) with filaments erect in the bud, and in the ♀-flower by the small, entire, cup-like perianth, which surrounds the base of the ovary (Fig. 346, p. 352). The ovary has two styles, or one divided into two, with two stigmas and a pendulous, curved ovule (Fig. 346 B, 352 B); the fruit is a nut; the embryo is curved (Hemp, Fig. 353), or rolled (Hop, Fig. 349), without endosperm.

Only 2 genera with 3 species (Asiatic), of which two are cultivated.—Humulus lupulus (Hop, Figs. 347–349) is a twining, perennial plant, twisting to the right, with opposite, palmilobed, rough leaves, and large, interpetiolar stipules. The ♀-flowers are situated in closely-flowered, cone-like, compound inflorescences, with ultimately large, thin, imbricate floral-leaves (Fig. 348) which bear the yellow, glandular hairs, containing lupulin. This inflorescence is made up as follows:—The most external floral-leaves are situated in pairs, and are the persistent stipules of a leaf, the blade of which has become suppressed, or in any case is rudimentary. Such a pair of stipules supports 4 (2–6) flowers in a double uniparous cyme, whose central axis does not develope into a flower. The bracts of these flowers (bracteoles of the partial inflorescence) become, at maturity, very large, spathe-like, and, together with the stipules, produce a cone-like appearance.