RHIZOPHORACE.E 763 



long and longer than the radial spines. Bark of the trunk and of the large branches 

 smooth, light brown or purple, usually unarmed, 3 '-4' thick, finally separating into small 

 closely appressed 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. 



XLVI. RHIZOPHORACEJE. 



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

 ing 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 seventeen genera confined to the Old 

 World. 



1. RHIZOPHORAL. Mangrove. 



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

 Leaves ovate or elliptic, glabrous, petiolate; stipules elongated, acuminate, .infolding the 

 bud, caducous. Flowers perfect, yellow or creamy white, sessile or pedicellate, bibracteo- 

 late, the bractlets united into an involucral cup, in pedunculate dichotomously or. trichoto- 

 mously branched clusters, the base of their branches surrounded by an involucre of 2 ovate 

 .'J-lobed persistent bracts, or 1-flowered ; calyx 4-lobed, the lobes acute, coriaceous, ribbed on 

 the inner surface and thickened on the margins, two or three times longer than the turbi- 

 nate globose tube, reflexed at maturity, persistent; petals 4, induplicate in the bud, alter- 

 nate 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 shorter 0; anthers attached at the base, 

 introrse, elongated, connivent, areolate; ovary partly inferior, conic, 2-celled, contracted 

 into two subulate spreading styles stigmatic at apex. Fruit a conic coriaceous berry sur- 

 rounded 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; coty- 

 ledons 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, one specie reaching those of 

 southern Florida. It possesses astringent properties; the bark has been used in tan- 

 ning leather, in dyeing, and as a febrifuge. The wood is hard, durable, and dark-col- 

 ored. By means of the aerial germination of its seeds and in its power to develop roots 

 from trunks and branches, Rhizophora is especially adapted to maintain itself on low tidal 

 shores and is an important factor in protecting and extending them into the ocean. Roots 

 springing from the stems at a considerable distance above the ground and arching out ward 

 descend into the water and fix themselves in the mud beneath, while roots growing down 

 from the branches enter the ground and gradually thicken into stems. The fully grown 

 radicle ready to put forth roots and leaves, and often 10'-12' long, is thicker and heavier 

 at the root end than at the other, and in detaching itself from the cotyledons and in falling 

 the heavy end sticks in the mud, while the plumule at the other end, held above the shal- 

 low surface of the water, soon unfolds its leaves. 



The generic name, from /Mfa and <}>tpeiv, was used by early authors to designate various 

 climbing plants with thickened roots. 



