1. THRINAX Sw.
Small unarmed trees, with stems covered with pale gray rind. Leaves orbicular, or truncate at the base, thick and firm, usually silvery white on the lower surface, divided to below the middle into narrow acuminate parted segments with thickened margins and midribs; rachis a narrow border, with thin usually undulate margins; ligule thick, concave, pointed, lined while young with hoary tomentum; petioles compressed, rounded above and below, thin and smooth on the margins, with large clasping bright mahogany-red sheaths of slender matted fibres covered with thick hoary tomentum. Spadix interfoliar, stalked, its primary branches short, alternate, flattened, incurved, with numerous slender rounded flower-bearing branchlets; spathes numerous, tubular, coriaceous, cleft and more or less tomentose at the apex. Flowers opening in May and June, and occasionally irregularly in the autumn, solitary, perfect; perianth 6-lobed; stamens inserted on the base of the perianth, with subulate filaments thickened and only slightly united at the base, or nearly triangular and united into a cup adnate to the perianth, and oblong anthers; ovary 1-celled, gradually narrowed into a stout columnar style crowned by a large funnel-formed flat or oblique stigma; ovule basilar, erect. Fruit a globose drupe with juicy bitter ivory-white flesh easily separable from the thin-shelled tawny brown nut. Seed free, erect, slightly flattened at the ends, with an oblong pale conspicuous subbasilar hilum, a short-branched raphe, a thin coat, and uniform albumen more or less deeply penetrated by a broad basal cavity; embryo lateral.
Thrinax is confined to the tropics of the New World and is distributed from southern Florida through the West Indies to the shores of Central America. Seven or eight species are now generally recognized.
The wood of the Florida species is light and soft, with numerous small fibro-vascular bundles, the exterior of the stem being much harder than the spongy interior. The stems are used for the piles of small wharves and turtle-crawls, and the leaves for thatch, and in making hats, baskets, and small ropes.
Thrinax, from θρῖναξ, is in allusion to the shape of the leaves.
CONSPECTUS OF THE NORTH AMERICAN SPECIES.
Flowers on elongated pedicels; perianth obscurely lobed; stamens much exserted, their filaments subulate, barely united at base; stigma oblique; cavity of the seed extending to the apex. Perianth obscurely lobed; style abruptly enlarged into a large oblique stigma; leaves silvery white on the lower surface.1. [T. floridana] (D). Perianth deeply lobed; style narrowed gradually into a small oblique stigma; leaves green on both surfaces.2. [T. Wendlandiana] (D). Flowers on short pedicels; lobes of the perianth ovate, acuminate; filaments nearly triangular, united below into a cup; stigma flat; cavity of the seed extending only to the middle. Seeds pale chestnut-brown; spadix about 6° long; leaves 3°—4° in diameter.3. [T. keyensis] (D). Seeds dark chestnut-brown; spadix less than 3° long; leaves not over 2° in diameter.4. [T. microcarpa] (D).
1. [Thrinax floridana] Sarg. Thatch.
Leaves 2½°—3° in diameter, rather longer than broad, yellow-green and lustrous on the upper surface, silvery white on the lower surface, with a long-pointed, bright orange-colored ligule ¾′ long and broad; petioles 4°—4½° long, pale yellow-green or orange color toward the apex, coated at first with hoary deciduous tomentum, much thickened and tomentose toward the base. Flowers: spadix 3°—3½° long, the primary branches 6′—8′ long and ivory-white, flower-bearing branches 1½′—2′ in length; flowers on slender pedicels nearly ⅛′ long, ivory-white, very fragrant, with an obscurely-lobed perianth, much exserted stamens barely united at the base, and a large stigma. Fruit ⅜′ in diameter, somewhat depressed at the ends; seed from ⅛′ to nearly ¼′ in diameter, dark chestnut-brown.
A tree, with a slightly tapering stem 20°—30° high and 4′—6′ in diameter, clothed to the middle and occasionally almost to the ground with the sheaths of dead leaf-stalks.
Distribution. Florida, dry coral ridges and sandy shores of keys from Long Key to Torch Key, and on the mainland from Cape Romano to Cape Sable.
2. [Thrinax Wendlandiana] Becc. Thatch.
Leaves 2½°—3° in diameter, orbicular, pale yellow-green, lustrous above, with a thick concave ligule, acuminate or rarely rounded at apex; petioles 2°—4° long, much thickened and tomentose toward the base. Flowers: spadix stalked, 2°—4° long, its primary branches short, flattened, incurved, with numerous terete flower-bearing branchlets; flowers on slender pedicels 1/10′—⅛′ long, with a deeply lobed perianth, the lobes nearly triangular, acuminate, and a small stigma. Fruit ¼′—⅜′ in diameter, globose; seed from ⅛′—¼′ in diameter, dark chestnut-brown.
A tree, in Florida, with a smooth pale trunk 20°—25° high and 3′—4′ in diameter.
Distribution. Florida: Dade County, Madeira Hummock, Pumpkin Key, Flamingo, and northwest of Cape Sable; also in Cuba and on Mugueres Island, Gulf of Honduras.
3. [Thrinax keyensis] Sarg. Thatch.
Leaves rather longer than broad, 3°—4° long, the lowest segments parallel with the petiole or spreading from it nearly at right angles, light yellow-green and lustrous on the upper surface, with bright orange-colored margins, below coated while young with deciduous hoary tomentum and pale blue-green and more or less covered with silvery white pubescence at maturity, with a thick pointed ligule 1′ long and wide, lined at first with hoary tomentum; petioles flattened above, obscurely ridged on the lower surface, tomentose while young, pale blue-green, 3°—4° long. Flowers: spadix usually about 6° long, spreading and gracefully incurved, with spathes more or less coated with hoary tomentum, large compressed primary branches, and short bright orange-colored flower-bearing branches; flowers on short thick disk-like pedicels, about ⅛′ long, white, slightly fragrant, with a tubular perianth, the lobes broadly ovate and acute, stamens with nearly triangular filaments united at the base, and a flat stigma. Fruit 1/16′ to nearly ¼′ in diameter; seed brown, 3/16′ in diameter.
A tree, with a stem often 25° high and 10′—14′ in diameter, raised on a base of thick matted roots 2°—3° high and 18′—20′ in diameter, and a broad head of leaves, the upper erect, the lower pendulous and closely pressed against the stem.
Distribution. Dry, sandy soil close to the beach on the north side of the largest of the Marquesas Keys, and on Crab Key, a small island to the westward of Torch Key, one of the Bahia Honda group, Florida; on the Bahamas.
4. [Thrinax microcarpa] Sarg. Silvertop Palmetto. Brittle Thatch.
Leaves 2°—3° across, pale green above, silvery white below, more or less thickly coated while young with hoary tomentum, especially on the lower surface, divided near the base almost to the rachis, with an orbicular thick concave ligule lined with a thick coat of white tomentum; petioles thin and flexuose. Flowers: spadix elongated, with short, compressed erect branches slightly spreading below, numerous slender pendulous flower-bearing branches, and long acute spathes deeply parted at the apex, coriaceous and coated above the middle with thick hoary tomentum; flowers on short thick disk-like pedicels, with a cupular perianth, the lobes broadly ovate and acute, stamens with thin nearly triangular exserted filaments slightly united at base and oblong anthers becoming reversed and extrorse at maturity, and a deep orange-colored ovary narrowed above into a short thick style dilated into a large funnel-formed stigma. Fruit globose, ⅛′ in diameter; seed subglobose, bright to dark chestnut-brown, depressed.
A tree, rarely more than 30° high, with a trunk 8′—10′ in diameter.
Distribution. Dry coral soil, on the shores of Sugar Loaf Sound, and on No Name and Bahia Honda keys, Florida; in Cuba.