Myriopiitllum. HALORAGEjE. 529 



times op])ositc or alteniate ; the submersed ones pinnatcly parted, with capil- 

 lary or filiform scrrnients. Flowers sessile in the axils of the upper loaves 

 (which are often reduced to bracts), bibracteolatc ; the uppermost usually 

 staminate, the lower fertile, and the intermediate often perfect. The stami- 

 nate flowers usually bear abortive pistils, and the pistillate often produce 

 sterile stamens. 



§ 1. Flowers octandrous : petals caducous: carpels not ridged on the lack: 

 leaves verlicillate. — Sjioiidyloiiliyllum. 



^-1. M. spicatum (Linn.) : leaves ternately verticillate, all pinnately parted 

 '^ with capillary segments; floral leaves (bracts) shorter than the flowers, ovate, 

 entire, the lowermost larger and serrate ; petals broadly ovate ; carpels 

 smootli and even. — Linn.! spec. 2. p)- 992; Michx. .' Jt." 2. p). 190; Fl. 

 Dan. f. 981 ; Engl. hot. t. 83 ; DC. ! prodr. 3. p. 68 ; Hook. ! fi. Bor.-Am. 

 I. p. 21 G. 



Deep ponds, Canada ! (from Bear Lake, Richardson) and Northern 

 States ! to Arkansas ! July-Aug. — Stem very long and slender, branching. 

 Floral leaves inconspicuous, whence the inflorescence appears as a terminal 

 interrupted leafless spike. Bracteoles triangular-ovate, about half the length 

 of the bract. Lobes of the calyx somewhat ol)tuse. Anthers oblong. 

 Stigmas short, pubescent along the inner side. — Water-J^lilfoil {Miile- 

 feuille.) 



2. M. vcrticillatum (Linn.) : leaves ternately verticillate, the lower ones 

 pinnately parted with capillary or setaceous segments ; floral leaves pecti- 

 nate-pinnatifid, commonly much longer than the flowers; petals oblong- 

 obovate ; carpels smooth and even. — Linn. ! I. c. ; Michx. ! fi. 2. p. 190 ; 

 Engl. hot. t. 218; Ell. sk. 2. p. 588 ; DC. I. c. 



In ponds and streams, Canada ! to Florida ? and Texas ! Oregon, Nut- 

 tall ! July-Sept. — Stem stouter than in M. si)icatum. Bracteoles minute- 

 Lobes of the calyx nearly lanceolate, acute, minutely serrulate. Anthers 

 oblong. Stigmas linear-oblong, at length woolly. — Water-Milfoil. 



§ 2. Flotcers tetrandrous {or hexandrous, according to Michaux and Elliott) : 

 petals sotnewhat persistent : carpels 1-2-ridged on the back: leaves verticil- 

 late. — Spondylastrum . 



3. M. heterophyllvm (Michx.) : stem tliick ; leaves mostly quinately 

 verticillate, the lower ones pinnately parted with attenuated capillary seg- 

 ments; floral leaves ovate or lanceolate (thick), sharply serrate, crowded ; 

 petals oblong; carpels minutely roughened, slightly 2-ridged and tuberculate 

 on the \mck.— Michx. ! fl. 2. p. 191 ; Pursh, fl. 1. p. 274; Ell. sk. 2. j?. 

 588 ; DC. ! prodr. 3. p. 69. Potamogeton vcrticillatum, Walt. Car. p. 90 ? 



In ponds and slow-flowing streams, Canada (near the Falls of Niagara !) 

 and New York ! to Florida! Louisiana! Arkansas! and Texas! June- 

 Sept. — Stem branching, often more than one-fourth of an inch in diameter 

 towards the base. Submersed leaves rather small ; the floral ones some- 

 times scattered, varying from ovate to linear-lanceolate ; the lowest pecti- 

 nate-pinnatifid. Bracteoles about the length of the petals, serrulate. Lobes 

 of the calyx minute, acute or acuminate. Petals at length somewhat 

 scarious and involute. Stamens (6, Michaux) 4 in all our specimens : 

 anthers linear. Carpels cohering at the axis merely. 



-J- 4. M. scabratum (Michx.) : stem rather slender ; leaves quaternately and 

 ' 67 



