The Mangroves (_Rhizophora_) are tropical trees, growing in the soft mud of rivers, particularly in that of the Niger, so that, when the rivers are full, they appear to grow out of the water. The seeds have the singular property of germinating in the capsule, and sending down long roots while yet hanging on the tree, the branches of which thus appear, at a little distance, as if covered with long white strings. All the genera belonging to this order require a stove in England. ORDER LXXV.—LOPHIREÆ. The only plant contained in this order is a beautiful shrub from Sierra Leone, with terminal corymbs of white flowers, and coriaceous leaves. ORDER LXXVI.—ONAGRARIÆ.—(SEE CHAP. IV. IN P. 75.) The tube of the calyx generally adheres to the ovary, and its limb is usually two or four lobed, the lobes frequently adhering together. The petals are either four, or equal in number to the lobes of the calyx; they are inserted in the mouth of the tube, and are twisted in the bud. The fruit is generally a capsule, or a berry, with two or four cells; and there are numerous seeds. The leaves vary considerably, and are sometimes alternate, and sometimes opposite, but never compound. De Candolle divides this order into six sections: viz. 1. _Montinieæ_; 2. _Fuchsieæ_; 3. _Onagreæ_, containing the Evening Primrose (_Œnothera_), and the French Willow Herb (_Epilobium_); 4. _Jussieuæ_; 5. _Circææ_, including the Enchanter’s Nightshade (_Circæa_), and _Lopezia_; and 6. _Hydrocaryes_, containing the Water-caltrops (_Trapa natans_). This last section is sometimes made a separate order. ORDER LXXVII.—HALORAGEÆ, OR CERCODIANÆ. Most of the plants in this order are British weeds; as for example, the Water Milfoil (_Myriophyllum_), Water Starwort (_Callitriche_), and Mare’s-tail (_Hippuris_); but some are natives of North America, China, &c., and one genus has lately been discovered in Australia, which Dr. Lindley has named _Loudonia aurea_, and which is a large shrub, with corymbs of golden yellow flowers. ORDER LXXVIII.—CERATOPHYLLEÆ. British weeds called Hornwort. ORDER LXXIX.—LYTHRARIEÆ, OR SALICARIÆ.