ONAGRACEJi:. 33 



of entire or closely pectinated bracts, which are shorter than the 

 flowers ; uppermost female flowers sometimes opposite or alternate ; 

 male flowers generally opposite or alternate, rarely whorled, in the 

 axils of bracts much sliorter than the flowers ; male portion of 

 spike hooked in bud, without a coma at the apex. Petals cadu- 

 cous. Anthers linear-oblong. Pruit ovoid-conical, truncate, longer 

 than broad before the separation of the carpels, which are not 

 ridged on the back. 



In ponds and ditches. 'Not uncommon and generally distri- 

 buted. In Scotland it seems to be more common than M. spicatum. 



England, Scotland, Ireland. Perennial. Summer 

 and Autumn. 



A more slender and delicate species than either of the preceding, 

 though much resembling M. spicatum in habit ; the leaves, how- 

 ever, are in closer whorls and with much shorter and more distant 

 segments ; the part of the spike which bears male flowers is hooked 

 while in bud ; the petals are yellow with red lines ; the fruit 

 smaller and narrower. The character taken from the male flowers 

 being alternate is not constant, they are nearly as often opposite 

 and sometimes whorled with 3 in a whorl. As in M. spicatum, the 

 lower part of the stem soon becomes bare of leaves for a consider- 

 able j)ortion of its length. 



A Iternate-Jloioered Water- Milfoil. 



French, Volant d)Eau a Fleurs AUernes. German, Wechselhluthiges Tausendblate. 



GENUS FJ— HIPPURIS. Li^m. 



Plowers perfect. Calyx completely adherent to the ovary, the 

 limb represented merely by a slightly elevated ring. Petals none. 

 Stamen 1, inserted on the rim of the calyx. Ovary 1-celled, with 

 1 pendulous ovule ; style papillose and stigmatiferous throughout 

 its whole length. Pruit herbaceous, 1-celled, 1-seeded. 



Aquatic herbs with creeping rhizomes, and whorled linear or 

 lanceolate entire leaves. Plowers whorled, sessile, axillary, very 

 minute, produced on the part of the stem which is out of the water. 



The name of this genus of plants is derived from tlie words [ir-Koc {hippos), a horse, 

 and ovpa {pura), a tail ; from the resemblance of the stem to a horse's tail. 



SPECIES I— HIPPURIS VULGARIS. Linn. 

 Plate DXVI. 

 Stem stout, erect. Leaves linear-strapshaped, to 12 in each 

 whorl, acute and sphacelate at the apex. 



VOL. IV. F 



