=ANDROPOGON= (from _aner_, a man, and _pogon_, a beard; tufts of hair

on flowers). ORD. _Gramineæ_. A large genus of grasses with polygamous

flowers. The majority of species are of no horticultural value;

several, however, are very ornamental subjects, and thrive well in

a rich, deep soil. Easily propagated by seeds or by division of the

roots. The South European kinds succeed in the open air if planted in

a warm dry border.

=A. citratum= (Citrus-leaved). Synonymous with _A. Schœnanthus_.

=A. Schœnanthus.= Lemon Grass. _fl._ in threes; spikes imbricate,

conjugate, panicled. A handsome species, the leaves of which emit

a very fragrant odour when bruised. _h._ 2ft. India, 1786. Stove

species. SYN. _A. citratum_.

Other species worth growing are _furcatus_, _halepensis_, _muricatus_,

_pubescens_, _scoparius_, _squarrosus_, and _strictus_.

=ANDROSACE= (from _aner_, a man, and _sakos_, buckler; in reference

to the resemblance of the anther to an ancient buckler). Including

_Aretia_. ORD. _Primulaceæ_. Dwarf annuals or perennials, entirely

alpine, agreeing in most characters with _Primula_, but having the

tube of the corolla narrowed at the mouth. An airy, well-drained,

and partially sunny position is essential in their culture. They

thrive well between fissures of rocks or stones with a rich sandy

peat soil. Drought and a sour soil are alike fatal, and both will be

greatly obviated if small pieces of sandstone are mixed with the soil.

The woolly species are best arranged beneath a jutting ledge of the

rockery, which will afford them protection from the hottest sunshine,

and from excessive wet in winter; additional comfort will be provided

from the latter ill if a piece of glass is placed over them during

the autumn and winter months. They can also be well grown, and make

charming little specimens, in pots, with rich sandy soil and thorough

drainage. Sprinkle sand among the small rosettes of leaves. They are

increased by divisions, cuttings, or seed; the latter should be sown as

early as possible, and raised in a frame.

=A. alpina= (alpine). _fl._ purplish rose; throat and tube yellow,

solitary; peduncles about 1/2in. long. June. _l._ crowded, small,

tongue-shaped, in small rosettes. _h._ 2in. to 3in. Switzerland,

1775. This species requires a rather shady aspect, and to be

planted almost perpendicularly in a soil composed of leaf mould,

peat, fibrous loam, and sharp sand. SYN. _A. glacialis_.

=A. Aretia= (Aretius'). Synonymous with _A. helvetica_.

=A. aretioides= (Aretia-like). Synonymous with _A. obtusifolia_.

=A. argentea= (silvery).* _fl._ white, sessile, very numerous.

June. _l._ densely imbricated, lanceolate, oblong, covered with

short hairs, forming very pretty silvery-grey rosettes. _h._

about 2in. Switzerland, 1826. This requires a well drained, sunny

fissure. SYN. _A. imbricata_.

=A. carnea= (flesh-coloured).* _fl._ pink or rose, with a

yellow eye, three to seven, on hairy stalked umbels. July. _l._

awl-shaped, smooth, acuminated, not forming rosettes. Stem somewhat

elongated. _h._ 3in. or 4in. Switzerland, 1768. This forms charming

little cushions if allowed to remain undisturbed; it is easily

increased. SYNS. _A. Lachenalii_, _A. puberula_.

=A. c. eximia= (select).* Larger and more robust than the typical

species, and a more rapid grower. Forms compact tufts of dense

rosettes, bearing heads of rosy-crimson yellow-eyed flowers, on

stems 2in. or 3in. high. Auvergne Alps, 1871. It requires moist

sunny ledges and fissures of rockwork in peat, loam, and sand.

=A. Chamæjasme= (rock jasmine).* _fl._ blush, ultimately deep pink,

with a yellow eye, umbellate. June. _l._ lanceolate, tapering

to a point towards the base, in comparatively large, not dense,

rosettes. _h._ about 2in. to 4in. Austria, &c., 1768. A very free

flowering species, growing freely when established, ultimately

forming large tufts. It thrives best in a deep, well drained and

rich loam soil.

=A. ciliata= (ciliated). _fl._ deep carmine red, on stems double as

long as the leaves. June. _l._ lanceolate-oblong, smooth on both

surfaces, with ciliated margins, imbricated. _h._ 2in. to 3in.,

forming dense cushions. Pyrenees.

=A. coronopifolia= (buckhorn-leaved).* _fl._ pure white, on slender

pedicels, umbellate on peduncles, about 6in. high. April to June.

_l._ lanceolate, distantly serrated, smooth, in flattish rosettes.

Russia, 1755. This is a charming little biennial, well worthy of a

place on the rockery. A colony of it is extremely pretty; it seeds

freely, and a batch of young plants almost invariably takes the

place of the old ones. SYN. _A. septentrionalis_.

=A. glacialis= (glacial). Synonymous with _A. alpina_.

=A. helvetica= (Swiss).* _fl._ white, nearly sessile, with a

yellow eye, larger than the little rosettes of leaves on the stalk

from which they spring. May. _l._ lanceolate, obtuse, closely

imbricated, small, ciliated. _h._ 1in., forming dense cushions.

Switzerland, 1775. A rare little gem, requiring a partially shaded

position, and very sandy soil. SYN. _A. Aretia_.

=A. imbricata= (imbricated). Synonymous with _A. argentea_.

=A. Lachenalii= (Lachenal's). Synonymous with _A. carnea_.

=A. lactea= (milk-white).* _fl._ pure white, with yellow throat,

large, on long graceful stalks, umbellate. June. _l._ linear,

or nearly so, in rosettes, sometimes scattered on the elongated

branches. _h._ about 4in. Austria, 1752. Very floriferous and

strong growing. Should have an eastern or western aspect, and be

propagated from seeds. SYN. _A. pauciflora_.

[Illustration: FIG. 90. ANDROSACE LAGGERI.]

=A. Laggeri= (Lagger's).* _fl._ pink, sessile; when approaching

maturity the stem becomes elongated, and bears a tuft of stalked

flowers. March. _l._ awl-shaped, sharply pointed, in tiny rosettes.

_h._ 3in. Pyrenees, &c., 1879. Very like _A. carnea_, but more

delicate, earlier, and more abundant flowering, with deeper green

foliage. It suffers from exposure to the sun, and therefore

requires a partially shady position. Should be propagated from

seeds or cuttings, which latter strike freely. See Fig. 90.

=A. lanuginosa= (woolly-leaved).* _fl._ delicate rose, with a

small yellow eye, umbellate. June to October. _l._ nearly 1in.

long, clothed with shiny silken hairs. _h._ 6in. to 9in. Himalaya,

1842. A very beautiful species, with spreading or trailing shoots,

easily multiplied by cuttings or layers. It requires a warm sunny

spot on the rockery, with a sandy peat soil. When planted so that

its shoots drape the face of a rocky ledge, it is one of the most

charming plants possible to grow.

A. obtusifolia (blunt-leaved). _fl._ white or rose, with yellow

eye; umbels five or six-flowered. Spring. _l._ lanceolate or

rather spathulate, in rather large rosettes. Stems downy. _h._

2in. to 6in. European Alps. A very pretty form, closely allied to

_A. Chamæjasme_, and differing principally in its somewhat larger

rosette of leaves and stronger growth. SYN. _A. aretioides_.

=A. pauciflora= (few-flowered). Synonymous with _A. lactea_.

=A. penicillata= (finely hairy). Synonymous with _A. villosa_.

=A. puberula= (puberulous). Synonymous with _A. carnea_.

=A. pubescens= (downy). _fl._ white, with a faint yellow eye,

solitary, at the ends of the branchlets, very numerous. June. _l._

oblong-ovate, ciliated, in a crowded rosette. Stem with a small

swelling close to the flower. _h._ 2in. Alps, 1869. Treat like _A.

Chamæjasme_.

=A. pyrenaica= (Pyrenean). _fl._ white, with yellowish eyes, on

a scape about 1/4in high. Summer. _l._ narrow-oblong, ciliated,

recurved, keeled at the back. _h._ 1in. Pyrenees. An exceedingly

pretty and diminutive little alpine plant, grown, according to Mr.

Robinson, "to great perfection in fissures between large rocks,

with, however, deep rifts of sandy peat and loam in them. It will

also grow on a level exposed spot, but in such a position should be

surrounded by half-buried stones."

=A. sarmentosa= (trailing).* _fl._ bright rose, with a white eye,

in umbels of ten to twenty, on an erect scape. May and June. _l._

very silvery, forming dense rosettes, whence spring a number of

runners, bearing at their extremities other tufts, which should

be pegged down and covered with soil, when they will root freely.

Himalayas, 1876. It requires rich sandy loam, a sunny position, and

to be wedged between pieces of sandstone. Cover the rosettes during

winter with a sheet of glass. See Fig. 91.

=A. septentrionalis= (northern). Synonymous with _A. coronopifolia_.

=A. villosa= (hairy).* _fl._ rose or blush, with a deeper coloured

eye, and a honey-like perfume, umbellate. May. _l._ narrow, oblong,

covered with soft white down, chiefly on the under surface, in

compact tufts. _h._ 2in. to 4in. Pyrenees, &c., 1790. When well

grown, the flowers are produced in great abundance, almost covering

the green cushions. Plant in a sunny fissure of the rockery, in

sandy loam and leaf soil. SYN. _A. penicillata_.

[Illustration: FIG. 91. ANDROSACE SARMENTOSA, showing Habit, and the

two kinds of Leaves, &c.]

=A. Vitaliana= (Vital's).* _fl._ rich yellow, comparatively large;

tube inflated at the middle, almost nestling among the leaves.

May to July. _l._ linear, acute, greyish. Stems numerous. _h._

1in. to 2in. Pyrenees, &c., 1787. When well grown, it produces

flowers in abundance, and is the only species in cultivation having

yellow flowers. A well-drained, sunny pocket is desirable, with a

calcareous soil, covering the surface with nodules of sandstone.

SYN. _Gregoria Vitaliana_.

=A. Wulfeniana= (Wulfen's).* _fl._ rosy or crimson, large. Summer.

_l._ oval, acuminated, in dense rosettes. _h._ 2in. Styria. A very

rare species in cultivation in this country.

=ANDROSÆMUM.= _See_ =Hypericum=.

=ANDROSTEPHIUM= (from _aner_, a man, and _stephos_, a crown; some

of the stamens are barren and petaloid, forming a corona). ORD.

_Liliaceæ_. A very pretty little hardy bulb, of dwarf habit, allied

to _Brodiæa_. It requires a rich sandy loam, in a sunny position, and

may be propagated by offsets and seeds; the latter should be sown as

soon as ripe in a cold frame. Plant 6in. deep, when it will require no

protection in winter.

=A. violaceum= (violet). _fl._ violet blue, about 1in. long, three

to six in an umbel, on pedicels about their own length; tube

infundibuliform, about as long as the spreading segments; corona

half as long. Spring. _l._ four to six, very narrow. _h._ 6in.

Texas, 1874.

=ANDRYALA= (the meaning of this is unknown). ORD. _Compositæ_. These

are pretty half-hardy evergreen herbaceous perennials, easily grown in

ordinary well-drained garden soil. Increased by seeds and divisions in

spring. Two species only are in cultivation.

=A. lanata= (woolly).* _fl.-heads_ yellow, Hieracium-like. May.

_l._ white, woolly, thick, oblong-ovate; radical ones stalked;

upper ones sessile. Stems with a leaf at each joint. _h._ about

1ft. South Europe, 1732.

=A. mogadorensis= (Mogador). _fl.-heads_ bright yellow, as large

as a half-crown; disk bright orange. April. Morocco, 1871. This

species is rare in cultivation.

=ANEILEMA= (from _a_, not, and _eilema_, involucre; in reference

to the absence of the involucre). ORD. _Commelynaceæ_. Greenhouse

and stove evergreen perennials, with generally a trailing habit.

A genus resembling _Commelyna_, from which it is distinguished by

the inflorescence being sub-paniculate, and the peduncles entirely

exserted from the bracts at the branching of the panicle. Flowers

without any involucre. They thrive in a compost of loam, peat, leaf

mould, and sand, well mixed. Increased by seeds and root divisions.

There are a large number of species known to botanists.

=A. biflora= (two-flowered).* _fl._ blue; floral stalks

two-flowered. July. _l._ lanceolate. Stem creeping; plant smooth.

New Holland, 1820. Greenhouse species.

=A. sinicum= (Chinese). _fl._ pale blue; racemes about

seven-flowered, alternate, placed in a panicle form. May. _l._

ligulate, acuminate. Stems branched, diffuse. _h._ 1ft. China,

1820. Greenhouse species.

=ANEMIA= (from _aneimon_, naked; in reference to the naked panicles of

sporangia). Including _Anemidictyon_. ORD. _Filices_. A well-marked

genus of stove and greenhouse ferns, chiefly confined to Tropical

America. Capsules small, very abundant, forming a copiously-branched

panicle, quite distinct from the leafy part of the frond. This genus

of handsome dwarf-growing ferns is of easy culture, in a compost of

fibrous peat, leaf soil, and sand. Several species are exceedingly

pretty for fern cases. For general culture, _see_ =Ferns=.

=A. adiantifolia= (maidenhair-leaved).* _sti._ 12in. to 18in. long,

firm, naked. _fronds_, barren portion shortly-stalked, 6in. to 9in.

long, 4in. to 6in. broad, deltoid, bi-tripinnate; pinnæ close,

lanceolate, the lowest the largest; ultimate divisions oblong or

linear-cuneate, the outer toothed, with a firm texture; panicle

3in. to 4in. long, the peduncle 1in. to 3in. long. West Indies,

1793. A very handsome stove fern.

=A. ciliata= (ciliated). Synonymous with _A. hirsuta_.

=A. collina= (hill). _sti._ 8in. to 12in. long, firm, erect,

densely clothed with fine ferruginous hairs. _fronds_, barren

portion sessile, 6in. to 12in. long, 2in. to 3in. broad, with about

twelve sessile pinnæ on each side, which are 1in. to 1-1/2in. long,

and about 1/2in. broad, unequal-sided, obliquely-truncate below,

blunt, sub-entire, with a sub-coriaceous texture; panicle 2in. to

3in. long, close, the peduncle 4in. to 6in. long. Brazil, 1829.

Very rare stove species. SYN. _A. hirta_.

=A. deltoidea= (deltoid-like). Synonymous with _A. tomentosa_.

=A. Dregeana= (Drege's).* _sti._ 8in. to 12in. long, firm, slightly

villose. _fronds_, barren portion sub-sessile, 8in. to 12in. long,

2in. to 3in. broad, about equal in width in the lower half, with

eight to twelve pinnæ on each side, which are 1in. to 1-1/2in.

long, 1/2in. to 3/4in. broad, ovate-deltoid, unequal at the base,

the upper side sub-cordate, the edge inciso-crenate; panicle 3in.

to 4in. long, the lower branches elongated; peduncle same length.

Natal. Stove species.

=A. flexuosa= (wavy). Synonymous with _A. tomentosa_.

=A. hirsuta= (hairy). _sti._ 6in. to 12in. long, slender, naked.

_fronds_, barren portion 2in. to 6in. long, 1in. to 3in. broad,

sessile, oblong-deltoid, bipinnatifid; pinnæ in six to eight

opposite pairs, 1in. to 1-1/2in. long, 1/4in. to 3/4in. broad,

varying from oblong, obtuse, sub-entire, truncate at the base on

the lower side, to deeply pinnatifid with narrow divisions; panicle

1in. to 2in. long, close; peduncle 2in. to 6in. long, slender.

Jamaica, 1704. Very handsome stove species. SYNS. _A. repens_ and

_A. ciliata_.

=A. hirta= (hairy). Synonymous with _A. collina_.

=A. mandioccana= (Mandioccan).* _sti._ 6in. to 12in. long,

deciduously villose. _fronds_, barren portion 1ft. or more long,

2in. to 4in. broad, oblong-lanceolate, the lower half about equal

in width; pinnæ in twenty or more close pairs, the point narrowed,

but scarcely acute; edge finely serrulate, the upper base parallel

with the stem, the lower obliquely truncate; rachis and surfaces

finely pilose; texture sub-coriaceous; panicle very compound,

3in. to 4in. long: peduncle longer. Brazil. A very beautiful and

distinct stove species.

=A. Phyllitidis= (Phyllitis-like).* _sti._ 6in. to 18in. long,

stramineous, naked, or fibrillose. _fronds_, barren portion

sessile, 4in. to 12in. long, 2in. to 8in. broad, ovate-oblong,

simply pinnate; pinnæ in four to twelve sessile pairs, the lowest

the largest, ovate, 1in. to 6in. long, 1/2in. to 2in. broad, the

apex acute, the edge crenulate, the base rounded or cuneate, or

unequal, with a firm texture; panicle dense, 3in. to 9in. long, the

branches short; peduncles the same length. Cuba, Mexico, &c. SYN.

_Anemidictyon Phyllitidis_. Greenhouse species.

=A. P. lineata= (lined). _fronds_ with a yellowish-green central

stripe down the pinnæ. South America, 1868.

=A. P. plumbea= (leaden). Synonymous with _A. P. tessellata_.

=A. P. tessellata= (tessellated). Pinnæ dark green, with bright

green centre and leaden-grey border. Brazil, 1875. The forms of

this species are numerous: _fraxinifolia_ and _macrophylla_ are

names often met with, but only show slight deviations. They all

have a more hardy constitution than the other species, and grow

well in the greenhouse. SYN. _A. P. plumbea_.

=A. repens= (creeping). Synonymous with _A. hirsuta_.

=A. tomentosa= (tomentose).* _sti._ 6in. to 12in. long, strong,

erect, clothed with ferruginous hairs. _fronds_, barren portion

6in. to 12in. long, half as broad, ovate-deltoid, bipinnatifid

or bipinnate; lowest pinnæ the largest, the blunt lobes 1/2in.

to 3/4in. long, 1/4in. broad, nearly entire; rachis and surfaces

densely pilose, with a firm texture; panicle 4in. to 9in. long,

loose; peduncle 1in. to 2in. long. Tropical America. Greenhouse

species. SYNS. _A. deltoidea_, _A. flexuosa_, _A. villosa_.

=A. villosa= (hairy). Synonymous with _A. tomentosa_.

=ANEMIDICTYON.= _See_ =Anemia=.

=ANEMONE= (from _anemos_, wind; the greater part of the species grow

in elevated places, much exposed to the wind). Wind Flower. ORD.

_Ranunculaceæ_. An extensive genus of very ornamental hardy perennials.

The generic characters of Anemone proper are: Involucre of three cut

leaflets, distant from the flower; calyx of five to twenty petal-like

sepals; petals absent. Of sub-genus Hepatica: Involucre of three entire

leaflets, just under the flowers; calyx of six to nine petal-like

sepals; petals absent. For botanical purposes, they are both now

included under the one generic name of Anemone; but in gardens the

Hepaticas are frequently regarded as a distinct genus. They delight in

a rich sandy loam, but most will thrive in ordinary garden soil. Some

are suitable for borders, while others thrive best on the rockery,

most of them preferring a damp and partially shady position. For the

numerous varieties of _A. coronaria_, both double and single flowered,

the soil can hardly be too rich, and the position, though open, should

be a sheltered one, and well drained. The tubers may be planted early

in October, about 6in. apart, and 3in. deep, various colours being

intermixed, when a splendid effect is produced in the following spring.

After flowering, the tubers should be taken up--say in June--and spread

out thinly, in a shady, airy situation, until they are dry, when they

should be thoroughly cleaned, and, if necessary, divided, and finally

stored away in a cool place, in pots or boxes of dry sand until the

planting season. Anemones make admirable pot plants if placed in a

compost of two parts turfy loam, and one of leaf mould or rotten hotbed

or cow manure, with about a sixth part of sharp gritty sand; but, if

so grown, they should be protected through severe weather, and brought

into warmth as required. The herbaceous species are propagated by root

divisions or root cuttings, or by seeds, in autumn or early spring;

the seeds are better sown as soon as ripe in pans in a cold frame.

Some, such as _A. japonica_, are freely increased by division; while

others, such as _A. narcissiflora_, are very slow; and the tuberous

rooted ones, by root division and seeds. The best and most rapid means

of propagating the invaluable varieties of _A. coronaria_, and also of

obtaining new ones, is by seed. A careful selection of flowers, and

skilful hybridising, will produce results commensurate with the trouble

incurred. So soon as the seed ripen, they should be gathered and sown

at once in a warm sheltered situation outside, or in pans under glass,

covering lightly with sandy soil, and keeping moist. They are somewhat

difficult to sow on account of a mass of cotton-like down which adheres

closely to them; they should be thoroughly separated therefrom by

rubbing them in dry sand. Of course, if the seed are sown at different

times, plants will be produced which will flower at different periods,

and a succession of bloom may be had from April to November--indeed,

nearly all the year.

=A. alba= (white). _fl._ white; pedicel solitary; sepals five,

obovate, very blunt. June. _l._ ternate or quinate; segments deeply

toothed at top; those of the involucre stalked. _h._ 6in. Siberia,

1820.

=A. alpina= (alpine).* _fl._ variously coloured, sometimes white,

white with the back purple, cream, yellowish or yellow with their

backs paler; sepals six, spreading, elliptical, rarely ovate. May.

_l._ sometimes smooth, sometimes clothed with long crowded silky

hairs, biternate; segments pinnate and deeply serrated; involucre

of the same form. _h._ 6in. Middle Europe, 1658. Very handsome

alpine. Plant on the rockery in rich deep soil, with a damp

situation. SYN. _Pulsatilla alpina_.

=A. a. sulphurea= (sulphur).* _fl._ beautiful soft yellow, 2in. to

2-1/2in. across when expanded, but they are usually cup-shaped;

sepals six, covered with a silky down outside; anthers of a rich

golden colour. May and June. _l._ radical, stalked, drooping,

more than 1ft. long; leaflets pinnatifid, deeply toothed. A very

beautiful form, thriving in ordinary garden soil, and a rather

moist situation. See Fig. 92.

[Illustration: FIG. 92. ANEMONE ALPINA SULPHUREA, showing Habit and

Flower.]

=A. americana= (American). A synonym of _A. Hepatica_.

=A. angulosa= (angled).* _fl._ fine sky blue, over 2in. across,

with numerous black anthers surrounding a tuft of yellow styles;

sepals eight to nine, elliptical, spreading. February. _l._

palmately five-lobed; lobes serrated. _h._ 8in. to 12in. East

Europe. A very fine species, twice the size of _A. Hepatica_ in all

its parts; it is well suited for the border or rockery, enjoying a

deep rich soil. SYN. _Hepatica angulosa_.

=A. apennina= (Apennine).* _fl._ blue, 1-1/2in. across; sepals ten

to fourteen, oblong, obtuse, erect; pedicel one-flowered. March.

_l._ binately pinnate; segments lanceolate, deeply-toothed, acute.

_h._ 6in. England (naturalised here and there), and Southern

Europe. An exceedingly pretty plant, with soft-looking feathery

foliage. It thrives best under the partial shade of trees, where

the flowers retain their colour longer. Tuberous rooted.

=A. baldensis= (Mount Baldo).* _fl._ white, clothed with adpressed

hairs on the outside, and reddish tinged with blue; sepals eight

to ten, oblong-oval; pedicels one-flowered. May. _l._ biternate;

segments many-parted; lobes linear; involucral leaves multifid.

_h._ 6in. Switzerland, 1792. _A. cœrulea_ is probably identical

with this species. Shady parts of the rockery. Rare. Tuberous

rooted.

=A. blanda= (fair).* _fl._ deep blue, nearly 2in. across; sepals

nine to fourteen, narrow. Winter or early spring. _l._ triternate;

segments deeply cut and acute; involucral leaves stalked, trifid,

deeply cut. _h._ 6in. Eastern Europe. A very handsome early

flowering plant. It requires a rich, light, and well drained sandy

loam, and a warm, sheltered position. It closely resembles _A.

apennina_, of which it is merely a form, with deeper blue flowers.

Tuberous rooted.

=A. caroliniana= (Carolina). _fl._ purple or whitish, pubescent

on the outside, on a long one-flowered pedicel; sepals ten to

twenty, oblong-linear. May. _l._ ternate, with three-parted, or cut

acutely-toothed lobes; involucral leaves trifid, with cut lobes.

_h._ 9in. Carolina, 1824. A very slender and delicate plant. Shady

parts of the rockery. Tuberous rooted.

=A. cernua= (drooping). _fl._ somewhat drooping, dark purple;

sepals six, spreading, elliptical-oblong. May. _l._ pinnate,

villous underneath; segments pinnatifid; lobes cut, oblong; scapes,

petioles, and peduncles clothed with downy hairs. _h._ 6in. Japan,

1806. Rare.

The Illustrated Dictionary of Gardening, Division 1; A to Car. A Practical and Scientific Encyclopædia of Horticulture · 第 21 / 72 段