XVIIl. ALISMACEiE. 799 



ovules many, covering the surface of the cell, or attached to a reticulate parietal 

 placenta, erect, anatropous {Butomus) or campylotropous {Limnocharis) . Caepels 

 distinct, coriaceous, usually beaked by the persistent styles, dehiscing ventrally 

 [Butomus) or dorsally (Limnocharis), many-seeded. Seeds erect, sometimes shortly 

 funicled, straight, with membranous testa (Butomus) ; sometimes sessile, hooked, 

 with a crustaceous transversely wrinkled testa [Limnocliaris). Embkto exalbuminous, 

 straight or hooked ; radicle inferior. 



PRINCIPAL GENERA. 

 * Butomus. Butomopsis. * Limnocharia. * Hydrocleis. 



Butomece are closely allied to Alismacece, through Limnocharis, only differing in their singular placeu- 

 tation and the numher of their ovules. 



This family is not numerous ; Butomus inhabits the north temperate zone, Limnocharis and Hydro- 

 cleis tropical America, Butomopsis Africa. The roots and seeds of Butomus umheUatus (Flowering Rush) 

 were formerly recommended as emollients and refrigerants. The baked root is still eaten in North Asia. 

 Hydrocleis is remarkable for its milky juice, and Limnocharis for the structure of its leaves, which have 

 a large terminal pore, by which the plant appears to relieve its tissues when gorged with liquid. This 

 phenomenon is identical with that described by Schmidt, Duchartre, and C. Musset, as occurring in 

 several Aroidece (Colocasia), and which consists in an intermittent more or less abundant emission of pure 

 water, to the extent of more than half an ounce in a hot summer's night, a phenomenon which has been 

 observed in the leaves of Graminea, and several other Monocotyledons. 



XVIII. ALISMACE^, Br. 



Flowers 3, or monoecious. Perianth 6-merous, 2-seriate (calyx and corolla). 

 Stamens hypogynous or perigynous, equal or m,uUiple in number with the perianth 

 leaflets. Ovaries more or less numerous, whorled or capitate, distinct, 1- celled, 1-2- 

 ovuled ; ovules campylotropous. Feuit a follicle. Seeds recurved, exalhuminous. 

 Bmbrto hooked. — Stem herbaceous. Leaves radical, strongly nerved. 



Aquatic or marsh heeds, perennial, sometimes producing subterranean tuber- 

 like buds (Sagittaria). Leaves usually radical, rosulate or fascicled; petiole with a 

 dilated sheathing base ; blade entire, nerves prominent, converging towards the top 

 and united by secondary transverse nerves, cordate or sagittate or oval-oblong, 

 arrested when the leaf is submerged, and then replaced by the petiole changed into 

 a linear or spathulate phyllode. Flowers regular, §, or rarely monoecious 

 (Sagittaria), in a raceme or panicle with whorled pedicels. Peeianth 6-phyllous, 

 leaflets 2-seriate, the 3 outer calycinal, the 3 inner petaloid, aestivation imbricate or 

 convolute caducous. Stamens inserted on the receptacle, or at the base and on 

 the sides of the inner perianth leaflets, equalling them or double or multiple in 

 number ; filaments filiform ; anthers 2 -celled, introrse, dorsifixed in the g flowers, 

 extrorse and basifixed in the g (Sagittaria), dehiscence longitudinal. Ovaries 6-8-00 , 

 whorled or capitate, quite distinct (Alisma, Sagittaria), or coherent by their ventral 

 suture (Damasonium); style ventral, very short; stigma simple; ovules campylo- 

 tropous, solitaryj basilar, erect (Alisma, Sagittaria), or 2-3 superimposed, the one 



