HALORAGIDACEAE (WATKR MILFOIL FAMILY) 603 



[*etals small or none. Stamens 1-8. Eruit indehiscent, 1-4-celled, with a 

 single aiiatropous seed suspended from the summit of each cell. Embryo in 

 the axis of ileshy albumen; cotyledons minute. 



i. Myriophyllum. Flowers monoecious or polygamous, the parts in fours, with or without 

 petals. Stamens 4 or 8. Leaves often whorled, the immersed commonly pinnately 

 rlissffterl. 



'i. Proserpinaca. l-'Iowers perfect, the parts in threes. Petals none. Leaves alternate, the 

 iiiimorsed pinnately dissected. 



8. Hippuris. Flowers apetalous. Stamen and style only one. Leaves entire, whorled. 



1. MYRIOPHYLLUM [Vaill.] L. Water Milfoil 



Mowers monoecious or polygamous. Calyx of the sterile flowers 4-parted, 

 of the fertile 4-tootlied. Petals 4, or none. Stamens 4-8. Fruit nut-like, 

 4-cened, deeply 4-lobed ; stigm.as 4, recurved. — Perennial aquatics. Leaves 

 crowded, often whorled ; those under water pinnately parted into capillary 

 divisions. Flowers sessile in the axils of the upper leaves, usually above water, 

 in summer ; the uppermost staminate, (Name from ^i)ptoi, numberless, and 

 (pijWov, a leaf, alluding, like Milfoil, to the innumerable divisions of the leaves.) 



w. Flowering stems leafy ; foliage leaves pectinate b. 



h. Flowers in terminal naked spikes or in the axils of greatly reduced or 

 modified leaves c. 

 c. Leaves in definite whorls d. 

 d. Leaves 5-12 mm. long ; flowers chiefly 1 or 2 at each node of the 



spike 1. 3L aU67m.iflorwm, 



d. Leaves chiefly longer ; flowers numerous, in remote verticels e. 

 6. Verticels apparently naked, the flor.al leaves shorter than or 

 only slightly exceeding the flowers. 

 Ehachis and segments of the foliage leaves capillary and of 



uniform diameteV ; floral leaves entire or merely dentate . 2. M, spicatim>., 

 Ehachis flattish and somewhnt broader than the segments of 



the foliage leaves ; floral ^ea^-es pectinate (3) M. Derticillaitt/tn, v. pecHnaium . 

 e. Yerticels subtended by elongate floral leaves /. 

 f. Petals quickly deciduous; stamens 8; carpels plump and 



rounded on the back S. M. v67-ticillatum. 



f. Petals tardily deciduous; stamens 4; carpels 1-2-ridged or 

 -angled on the back. 

 Floral leaves ovate to oblanceolate ; carpels papillose- 

 roughened 4. Jlf. heterophylluvi. 



Floral leaves linear or linear-lanceolate ; carpels smooth , 5. M. hippuroides. 

 o. Leaves variously arranged (verticillate, falsely verticillate, oppo- 

 site, or alternate) on the same plant. 

 Carpels with flat sides and tuberculate-ridged back . . . 6. Jf. sGabratum. 

 Carpels plump, smooth or minutely papiflose . . . . 8. M. humile. 



b. Flowers in the axils of unmodified foliage leaves. 



Carpels smooth or barely papillose, plump, not ridged on the back . 8. M. fiiMnile. 

 Carpels with flat sides and prominent tuberculate dorsal ridges. 



Fruit 2-2.5 mm. long 1. M, Farwellii. 



Fruit 1-1.5 mm. long 6. M. scabraium. 



a. Flowering steins naked or %vith few scattered filiform uncleft leaves . 9. M. tenellum. 



§ 1. PENTApTERIS DC. Stamens 8 ; petals early deciduous ; leaves whorled. 

 * Floral leaves (bracts) scattered; flowers rarely in verticels. 



1. M. alterniflbrum DC. Very slender ; leaves 5-12 mm. long, the rhachii! 

 and' segments capillary ; floioers solitary or in pairs, in simple or branched 

 nearly naked spikes ; lowermost bracts pectinate, the others entire or nearly so, 

 shorter than the flowers. — Ponds and slow streams, Nfd. to Ont., s, to Middlese:j4 

 Co., Mass., and L. Champlain, Vt. (Greenl., Eu.) 



*• * Floral leaves and flowers in verticels. 



2. M. spic£ltum L. Leaves somewhat rigid, 1-3 cm. long., the rhachis and 



capillary segments of uniform diameter; flowers verticillate, in an interrupted 



apparently naked spike; the bracts shorter than or slightly exceeding the flowers, 



entire or merely dentate; stigmas roundish, closely sessile, not elongated ; sepals 



