ALISMACE^. 75 



England. Perennial (?). Summer, Autumn. 



Tiootstock a slightly thickened corm, producing tufts of radical 

 leaves on scapes which flower in succession. Leaves stalked, floating 

 when the plant grows in water, ascending or erect when on mud ; 

 petiole variable in length ; lamina 1 to 3 inches long, 3- to 5-nervc(l, 

 nsually slightly cordate at the base, obtuse, when floating resembling 

 the leaves of Potamogeton polygonifolius, but of a brighter green. 

 Scapes leafless, 3 inches to 2 feet high, bearing a raceme of usually 2 or 

 3 whorls of flowers with membranous bracts at the base of the pedicels, 

 which are generally numerous in eacli whorl, and lengthen after 

 flowering until they are 1 to 2 inches long. Flowers about |- inch 

 across; outer perianth leaves green, deciduous; inner ones white with 

 a yellow spot at the claw, very caducous. Fruit of 6 (more rarely 5 

 to 8) follicles, united at the base and Avith subulate beaks spreading 

 like the spokes of a wheel, but slightly ascending, each follicle about 

 ^ inch long, opening at length by the ventral suture. Seeds narrowly 

 oblong, gi'ooved, transversely-rugose, pitchy-chestnut colour, about yL- 

 inch long, normally 2, but often only 1 by the abortion of the second 

 ovule. 



Thrum Wort. 



Frencb, FlCdeau eioile. 



Sub-Order III.— BUT0MEJ5. 



Perianth with the segments all nearly similar and petaloid, or the 

 3 outer ones herbaceous. Stamens 9 or more. Ovules numerous in 

 each cell of the ovary. Embryo straight or hooked. 



GENUS F/.— BUTOMUS. Toumef. 



Perianth of 6 persistent concave petaloid segments ; the outer ones 

 subherbaceous on the back. Stamens 9, subhypogynous, in pairs 

 opposite the outer perianth segments, and solitary opposite the inner 

 ones ; filaments narrowly subulate. Ovary consisting of a whorl of six 

 1-celled carpels cohering at the base; ovules numerous in each car2>el; 

 styles forming a beak to the carpels ; stigmas simjjle. Fruit of G 

 follicles, cohering at the base, opening by the ventral suture. 



A marsh herb with radical linear somewhat bayonet-shaped leaves, 

 and simple cylindrical scapes bearing a bracteated umbel of numerous 

 rose-coloured flowers. 



The derivation of the name of this genus of plants is from /joi/c, ox, and TtavUf I cut, 

 l)emg supposed to injm-e the mouths of cattle. 



1.2 



