Trees, growing by a single terminal bud, with stems covered with a thick rind, usually marked below by the ring-like scars of fallen leaf-stalks, and clothed above by their long-persistent sheaths; occasionally stemless. Leaves clustered at the top of the stem, plaited in the bud, fan-shaped or pinnate, their rachis sometimes reduced to a narrow border, long-stalked, with petioles dilated into clasping sheaths of tough fibres (_vaginas_); on fan-shaped leaves, furnished at the apex on the upper side with a thickened concave body (_ligule_). Flowers minute, perfect or unisexual, in the axils of small thin mostly deciduous bracts, in large compound clusters (_spadix_) surrounded by boat-shaped bracts (_spathes_); sepals and petals free or more or less united; stamens usually 6; anthers 2-celled, introrse, opening longitudinally; ovary 3-celled, with a single ovule in each cell; styles 1—3. Fruit a drupe or berry; embryo cylindric in a cavity of the hard albumen near the circumference of the seed. Of the 130 genera now usually recognized and chiefly inhabitants of the tropics, seven have arborescent representatives in the United States. CONSPECTUS OF THE NORTH AMERICAN ARBORESCENT GENERA. Leaves fan-shaped. Leaf-stalks unarmed. Calyx and corolla united into a short 6-lobed perianth. Fruit white, drupaceous; albumen even. 1. Thrinax. Fruit black, baccate; albumen channeled. 2. Coccothrinax. Calyx and corolla distinct; fruit baccate. 3. Sabal. Leaf-stalks armed with marginal spines. Filaments slender, free; fruit baccate. 4. Washingtonia. Filaments triangular, united into a cup adnate to the base of the corolla; fruit drupaceous. 5. Acœlorraphe. Leaves pinnate. Flower-clusters produced on the stem below the leaves; fruit violet-blue. 6. Roystonea. Flower-clusters produced from among the leaves; fruit bright orange-scarlet. 7. Pseudophœnix. 1. THRINAX Sw.