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See also:LABIATAE (i.e. " lipped," See also:Lat. labium, See also:lip) , in See also:botany, a natural See also:order of See also:seed-See also:plants belonging to the See also:series Tubiflorae of the See also:dicotyledons, and containing about 150 genera with 2800 See also:species . The See also:majority are See also:annual or perennial herbs inhabiting the temperate See also:zone, becoming shrubby in warmer climates . The See also:stem is generally square in See also:section and the See also:simple exstipulate leaves are arranged in decussating pairs (i.e. each pair is in a See also:plane at right angles to that of the pairs immediately above and below it) ; the blade is entire, or toothed, lobed or more or less deeply cut . The plant is often hairy, and the hairs are frequently glandular, the secretion containing a See also:scent characteristic of the genus or species . The See also:flowers are See also:borne in the axils of the leaves or bracts; they are rarely solitary as in Scutellaria (See also:skull-cap), and generally See also:form an apparent whorl (verticillaster) at the See also:node, consisting of a pair of cymose inflorescences each of which is a simple three-flowered dichasium as in Brunella, See also:Salvia, &c., or more generally a dichasium passing over into a pair of monochasial cymes as in Lamium (fig . I), Ballota, Nepeta, &c . A number of whorls may be crowded at the See also:apex of the stem and the subtending leaves reduced to small bracts, the whole forming a raceme- or spike-like inflorescence as in Mentha (fig . 2, 5) Brunella, &c.; the bracts are sometimes large and coloured as in Monarda, species of Salvia, &c., in the latter the apex of the stem is sometimes occupied with a cluster of sterile coloured bracts . The See also:plan of the See also:flower is remarkably See also:uniform (fig . 1, 3); it is bisexual, and zygomorphic in the median plane, with 5 sepals See also:united to form a persistent See also:cup-like calyx, 5 petals united to form a two-lipped gaping corolla, 4 stamens inserted on the corolla-See also:tube, two of which, generally the anterior pair, are longer than the other two (didynamous arrangement)—sometimes as in Salvia, the posterior pair is aborted—and two See also:superior median carpels, each very See also:early divided by a constriction in a See also:vertical plane, the See also:pistil consisting of four cells each containing one erect anatropous ovule attached to the See also:base of an See also:axile See also:placenta; the See also:style springs from the centre of the pistil between the four segments (gynobasic), and is simple with a bifid apex . The See also:fruit comprises four one-seeded nutlets included in the persistent calyx; the seed has a thin testa and the embryo almost or completely fills it . Although the See also:general form and plan of arrangement of the flower is very uniform, there are wide See also:variations in detail . Thus the calyx may be tubular, See also:bell-shaped, or almost spherical, or straight or See also:bent, and the length and form of the See also:teeth or lobes varies also; it may be equally toothed as in See also:mint (Mentha) (fig . 2, 3), and See also:marjoram (Origanum), or two-lipped as in See also:thyme (Thymus), Lamium (fig . 1) and Salvia (fig . 2, 1); the number of nerves affords useful characters for distinction of genera, there are normally five See also:main nerves between which simple or forked secondary nerves are more or less See also:developed . The shape of the corolla varies widely, the See also:differences being doubtless intimately associated with the See also:pollination of the flowers by See also:insect-agency . The tube is straight or variously bent and often widens towards the mouth . Occasionally the See also:limb is equally five-toothed, or forms, as in Mentha (fig . 2, 3, 4) an almost See also:regular four-toothed corolla by See also:union of the two posterior teeth . Usually it is two-lipped, the upper See also:lip being formed by the two posterior, the See also:lower lip by the three anterior petals (see fig. r, and fig . 2, 1, 6); the median See also:lobe of the lower lip is generally most developed and forms a resting-See also:place for the See also:bee or other insect when probing the flower for See also:honey, the upper lip shows See also:great variety in form, often, as in Lamium (fig . 1), Stachys, &c., it is arched forming a See also:protection from See also:rain for the stamens, or it may be See also:flat as in thyme . In the tribe Ocimoideae the four upper petals form the upper lip, and the single anterior one the lower lip, and in Teucrium the upper lip is absent, all five lobes being pushed forward to form the lower . The posterior stamen is sometimes See also:present as a staminode, but generally suppressed; the upper pair are often reduced to staminodes or more or less completely suppressed as in Salvia (fig . 2, 2, 6) ; rarely are these developed and the anterior pair reduced . In See also:Coleus the stamens are monadelphous . In Nepeta and allied genera the posterior pair are the longer, but this is rare, the didynamous See also:character being generally the result of the anterior pair being the longer . The anthers are two-celled, each See also:cell splitting lengthwise; the connective may be more or less developed between the cells; an extreme See also:case is seen in Salvia (fig . 2, 2), where the connective is filiform and jointed to the filament, while the anterior anther-cell is reduced to a sterile appendage . Honey is secreted by a hypogynous disk . In the more general type of flower the anthers and stigmas are protected by the arching upper lip as in dead-See also:nettle (fig . 1) and many other See also:British genera; the lower lip affords a resting-place for the insect which in probing the flower for the honey, secreted on the lower See also:side of the disk, collects See also:pollen on its back . Numerous variations in detail are found in the different genera; in Salvia (fig . 2), for instance, there is a See also:lever mechanism, the barren See also:half of each anther forming a knob at the end of a See also:short See also:arm which when touched by the See also:head of an insect causes the anther at the end of the longer arm to descend on the insect's back . In the less See also:common type, where the anterior See also:part of the flower is more developed, as in the Ocimoideae, the stamens and style See also:lie on the under lip and honey is secreted on the upper side of the hypogynous disk; the insect in probing the flower gets smeared with pollen on its belly and legs . Both types include brightly-coloured flowers with longer tubes adapted to the visits of butterflies and moths, as species of Salvia, Stachys, Monarda, &c.; some See also:South See also:American species of Salvia are pollinated by humming-birds . In Mentha (fig . 2, 3), thyme, marjoram (Origanum), and allied genera, the flowers are nearly regular and the stamens spread beyond the corolla . The persistent calyx encloses the ripe nutlets, and See also:aids in their See also:distribution in various ways, by means of winged spiny or hairy lobes or teeth; sometimes it forms a swollen See also:bladder . A scanty endosperm is sometimes present in the seed; the embryo is generally parallel to the fruit See also:axis with a short inferior radicle and generally flat cotyledons . The order occurs in all warm and temperate regions; its See also:chief centre is the Mediterranean region, where some genera such as Lavandula, Thymus, Rosmarinus and others form an important feature in the vegetation . The tribe Ocimoideae is exclusively tropical and subtropical and occurs in both hemispheres . The order is well represented in See also:Britain by seventeen native genera; Mentha (mint) including also M. piperita (See also:peppermint) and M . Pulegium (See also:pennyroyal) ; Origanum vulgare (marjoram) ; Thymus Serpyllum (thyme) ; Calamintha (calamint), including also C . Clinopodium (See also:wild See also:basil) and C . Acinos (basil thyme) ; Salvia (See also:sage), including S . Verbenaca (clary) ; Nepeta Cataria (catmint), N . Glechoma (ground-See also:ivy) ; Brunella (self-heal) ; Scutellaria (skull-cap) ; Stachys (woundwort) ; S . Betonica is See also:wood betony; Galeopsis (See also:hemp-nettle) ; Lamium (dead-nettle) ; Ballota (See also:black See also:horehound) ; T,eucrium (germander) ; and Ajuga (See also:bugle) . See also:Labiatae are readily distinguished from all other orders of the series excepting Verbenaceae, in which, however, the style is terminal; but several genera, e.g . Ajuga, Teucrium and Rosmarinus, approach Verbenaceae in this respect, and in some genera of that order the style is more or less sunk between the ovary lobes . The fruit-character indicates an See also:affinity with See also:Boraginaceae from which, however, they differ in See also:habit and by characters of ovule and embryo . The presence of volatile oil renders many genera of economic use, such are thyme, marjoram (Origanum), sage (Salvia), See also:lavender (Lavandula), See also:rosemary (Rosmarinus), patchouli (Pogostemon) . The tubers of Stachys Sieboldi are eaten in See also:France . |
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