428 ALISMACE^E. [DAMASONIUM. 



Gravelly ditches and pools, rare, from Salop and Suffolk to Kent and Hants ; 

 fl. May-July. Leaves many, 2 in., obtuse, floating or emersed; petiole stout, 

 2-5 in. Scape 4-6 in., stout, with usually 2 whorls of flowers ; pedicels 1 in. 

 Flowers J in. diam. ; petals caducous. Fruit in. diam., carpels dehiscing 

 ventrally. DISTRIB. France, Spain, Italy, N. Africa. 



4. SAGITTA'RIA, L. 



Habit and inflorescence of Alls' ma, but flowers 1 -sexual ; stamens 

 numerous ; anthers basifixed, dehiscence lateral. DISTRIB. Temp, and 

 trop. ; species about 15. ETYM. sagitta, an. arrow. 



S. sagittifo'lia, L. ; leaves hastate obtuse or acute. Arrow-head. 

 Ditches, canals, &c., from Cumberland to Kent and Devon ; naturalized in 

 Scotland ; local in Ireland ; fl. July-Sept. Stem swollen at the base, stoloni- 

 ferous ; stolons producing globose winter tubers in. diam. Leaves 2-8 in., 

 erect, lobes long more or less diverging acuminate, the first developed sub- 

 merged, pellucid, linear ; petiole 8-18 in., stout, 3-gonous. Scape 6-18 in., 

 with 3-5 distant whorls of 3-5 flowers each ; bracts short, obtuse, mem- 

 branous; lower whorls female, pedicels short; upper male with longer 

 pedicels. Flowers \ in. diam., males larger. Petals white, caducous, claw 

 purple. Anthers purple. Ripe carpels numerous, much compressed laterally, 

 obliquely obovate, apiculate, wings broad thick, cell small. Seeds as in 

 Alis' ma. DISTRIB. Europe (Arctic) (excl. Greece), N. Asia, N.W. India. 



5. BU'TOMUS, L. FLOWERING EUSH. 



A tall marsh herb, Rootstoek creeping. Leaves slender, erect. Scape 

 naked. Flowers in a bracteate umbel. Perianth- segments 6, oblong, 

 spreading, subequal, all coloured. Stamens 9, hypogynous, 6 in pairs 

 opposite the outer segments, 3 opposite the inner, filaments subulate ; 

 anthers basifixed, oblong, introrse. Carpels 6, beaked, connate below ; 

 styles short, stigmas sessile ; ovules covering the walls of the' carpel, 

 auatropous, ascending. Follicles 6, beaked, coriaceous, turgid. Seeds 

 many, minute, ascending, testa thin furrowed ; embryo straight. DISTRIB. 

 Europe, 1ST. and W. Asia, N.W. India. ETYM. obscure. 



B. umbella'tus, L. ; leaves long slender 3-quetrous, scape terete. 



Ditches and river-sides from York and Durham southd. ; naturalized in Scot- 

 land ; rare in Ireland ; fl. June-July. Rootstoek stout. Leaves 3-4 ft., base 

 sheathing, twisted. Flowers many, 1 in. diam., rose-red, proterandrous ; 

 pedicels 2-4 in. Anthers and carpels red. 



ORDER LXXXVII. NAlADA'CE-ffl. 



Marsh- or water-herbs. Rootstoek usually creeping. Stems elongate 

 (rarely 0), jointed, branched, slender. Leaves often floating, alternate 

 or distichous, rarely opposite, G sheathing at the base ; stipules 



