RHIZOPHORACE^ 691 



sheaths, 4-14 and on old tubercles 20-25 in number, the inner 1-4 in number, usu- 

 ally deflexed and unequal in length, the longest about ^' long and longer than the 

 radial spines. Bark of the trunk and of the large branches smooth, light brown 

 or purple, usually unarmed, ^'|' thick, finally separating into small closely ap- 

 pressed black scales. Wood reticulate, hard, compact, light reddish brown and 

 rather lustrous, with thin conspicuous medullary rays, well-defined layers of annual 

 growth, and thick pale or nearly white sapwood. 



Distribution. Foothills and low mountain slopes of southern Arizona and 

 northern Sonora; very abundant. 



XLIV. RHIZOPHORACE.ffl. 



Glabrous trees or shrubs, with terete branchlets, and usually opposite cori- 

 aceous entire persistent leaves with interpetiolar stipules. Flowers in axillary 

 clusters; calyx-lobes valvate in the bud, persistent; petals inserted on the 

 tube of the calyx and as many as its lobes ; stamens inserted at the base of a 

 conspicuous disk ; anthers 2-celled, the cells opening longitudinally ; pistil of 

 2-5 united carpels ; ovary 2-5-celled ; ovules usually 2 in each cell, suspended 

 from its apex, collateral, anatropous ; raphe ventral ; micropyle superior. 

 Fruit usually indehiscent, 1-celled and 1-seeded. 



The Mangrove family is tropical, with most of its fifteen genera confined to 

 the Old World, one species of the widely distributed Rliizophora reaching the 

 shores of southern Florida. 



1. RHIZOPHORA, L. Mangrove. 



Trees, with pithy branchlets, thick astringent bark, and adventitious fleshy roots. 

 Leaves ovate or elliptical, glabrous, petiolate; stipules elongated, acuminate, in- 

 folding the bud, caducous. Flowers perfect, yellow or creamy white, sessile or 

 pedicellate, bibracteolate, the bractlets united into an involucral cup, in pedunculate 

 (lichotomously or trichotomously branched clusters, the base of their branches sur- 

 rounded by an involucre of 2 ovate 3-lobed persistent bracts, or 1-flowered; calyx 

 4-Iobed, the lobes acute, coriaceous, ribbed on the inner surface and thickened on the 

 margins, two or three times longer than the turbinate globose tube, reflexed at ma- 

 turity, persistent; petals 4, induplicate in the bud, alternate with and longer than 

 the calyx-lobes, inserted on a fleshy disk-like ring in the mouth of the calyx-tube, 

 involute on the margins, coated on the inner surface with long pale hairs, or flat and 

 naked, caducous; stamens 8-12; filaments short or 0; anthers attached at the 

 base, introrse, elongated, connivent, areolate; ovary partly inferior, conical, 2-celled, 

 contracted into two subulate spreading styles stigmatic at the apex. Fruit a conical 

 coriaceous berry surrounded by the reflexed calyx-lobes and perforated at the apex 

 by the germinating embryo. Seed germinating in the fruit before falling, the apex 

 surrounded by a thin albuminous cup-like aril; seed-coat thick and fleshy; embryo 

 surrounded by a thin layer of albumen; cotyledons dark purple; radicle elongated, 

 clavate, and when fully grown separating from the narrow exserted woody tube 

 inclosing the plumule and developed from the cotyledons after the ripening of the 

 fruit. 



Rhizophora with three species is widely and generally distributed on the shores of 

 tidal marshes in the tropical regions of the two hemispheres. It possesses astrin- 

 gent properties; the bark has been used in tanning leather, in dyeing, and as a 



