2. AVICENNIA L.
Trees, with coriaceous persistent leaves, stout pithy branches thickened at the nodes and marked by interpetiolar lines, and long thick horizontal roots producing numerous short vertical thick and fleshy leafless stems rising above the surface of the soil. Flowers opposite, cymose, in centripetal pedunculate spikes or heads, closely invested by a bract and 2 bractlets, the peduncles solitary or in pairs in the axils of upper leaves and ternate on the end of the branches, their bracts and bractlets concave, acute, apiculate, keeled on the back, scarious, slightly ciliate on the margins, shorter than the corolla, persistent under the fruit; calyx cup-shaped, coated like the bracts and bractlets with canescent pubescence, divided nearly to the base into 5 concave ovate rounded lobes imbricated in the bud; corolla campanulate, white, with a straight cylindric tube shorter than the glabrous or tomentose spreading 4-lobed limb, the posterior lobe usually larger than the others; stamens exserted; filaments short, filiform, slightly thickened at base; anthers ovoid; ovary ovoid, pubescent, 1-celled, gradually narrowed into an elongated slender style divided at apex into 2 lobes stigmatic on their inner face; ovules 4, suspended from the summit of a free central placenta, orthotropous, naked. Fruit an ovoid oblique compressed 1-seeded capsule apiculate at apex; pericarp thin, light green, villose-pubescent on the outer surface, longitudinally veined on the inner surface, opening by the ventral suture and displaying the embryo enlarging before separating from the branch, ultimately 2-valved. Seed naked, without albumen; embryo filling the cavity of the fruit, light green; cotyledons thick and fleshy, broader than long, slightly pointed, deeply cordate at base, unequal, conduplicate; radicle elongated, clavate, retrorsely hirsute, inferior, descending obliquely and included between the lobes of the cotyledons slightly attached near the apex in the bottom of the capsule to the withered columella by a minute papillose point; plumule hairy.
Avicennia with three species is widely distributed on maritime shores of the tropics of the two worlds, with one species reaching those of the southern United States. Avicennia produces hard strong wood. The bark is rich in tannic acid, and is used for tanning leather. The chief value of these trees is in their ability to live on low tidal shores by the structure of the embryo, which is growing and ready to take root as soon as it falls into the soft mud, and in the long horizontal roots furnished with short vertical fleshy leafless branches or aerating roots, forming a close network which holds the soil together and prevents it from being washed away by outflowing tides, and extends the growth of the tree by numerous stems which soon form dense thickets.
The generic name is in honor of the illustrious physician of the Orient, Avicenna of Bokhara (980—1036).
1. [Avicennia nitida] Jacq. Black Mangrove.
Leaves oblong or lanceolate-elliptic, rounded or acute at apex and gradually narrowed at base, dark green and often lustrous above, hoary-tomentulose below, 2′—3′ long and ¾′—1½′ wide, with slightly thickened revolute margins, a broad midrib thickened and grooved toward the base on the upper side, and oblique primary veins arcuate and joined close to the margins, conspicuous on the 2 surfaces, and connected by prominent reticulate veinlets; appearing irregularly and falling early in their second season; petioles broad, channeled, enlarged at base, and about ½′ in length. Flowers produced continuously throughout the year, their bracts and bractlets nearly ¼′ long, coated with pale or slightly rufous pubescence and about as long as the lobes of the calyx, in few-flowered short spikes on stout 4-angled canescent peduncles ½′—1½′ in length, the lateral peduncles of the ternate terminal cluster subtended by oblong acute bracts ½′ long; corolla ½′ across the expanded slightly tomentose lobes, and nearly closed in the throat. Fruit 1′—1½′ long and ¾′—1′ wide.
A tree, occasionally 60°—70° high, with a short trunk rarely 2° in diameter, spreading branches forming a broad round-topped head, and branchlets at first slightly angled, coated with fine hoary deciduous pubescence, and light orange color, becoming in their second year more or less contorted, light or dark gray, conspicuously marked by the interpetiolar lines and by horizontal leaf-scars displaying a central row of fibro-vascular bundle-scars; usually not more than 20°—30° tall, with a short slender stem, and toward the northern limit of its range a low shrub. Bark of the trunk ¼′—½′ thick, roughened with thin irregularly appressed dark brown scales tinged with red, and in falling displaying the bright orange-red inner bark. Wood very heavy, hard, rather coarse-grained, with numerous medullary rays and eccentric layers of annual growth, dark brown or nearly black, with thick brown sapwood.
Distribution. Florida, St. Augustine to the southern keys on the east coast, and from Cedar Keys to Cape Sable on the west coast; on some of the islands in Mississippi Sound, and on the shore of Terrebonne and Cameron Parishes, and on most of their islands, Louisiana; on the Bahama Islands, on many of the Antilles, and southward to Brazil; and on the west coast of Africa; in the United States of its largest size in Florida just north of Cape Sable; north of Matanzas Inlet on the east coast of Florida usually with stems only a few feet tall.