1. E. parvulus, Engelm. Scapes 1--3' high; shoots often creeping and proliferous; _leaves lanceolate or spatulate, acute_ (--1' long, including the petiole); umbel single, 2--8-flowered; pedicels reflexed in fruit; flower 3" broad; _stamens 9; styles much shorter than the ovary; achenes beakless_, obtusely few-ribbed.--In mud, Ma.s.s. to Mich.

and E. Minn., south to Fla. and Tex. (S. Am.)

2. E. rostratus, Engelm. _Scape erect_, 3'--2 high, longer than the leaves; _leaves broadly ovate, cordate or truncate at base, obtuse_ (the blade 1--3' long); umbel proliferous, in a branched panicle; flower 5"

broad; _stamens 12; styles longer than the ovary; achenes beaked_, acutely many-ribbed.--Swamps and ditches, Ill. to Fla., Mo., and Tex.--A low form (var. LANCEOLaTUS, Engelm.) has the leaves lanceolate with an acute base. Ill., Mo.

3. E. radcans, Engelm. _Stems or scape prostrate, creeping_ (2--4 long), proliferous, bearing many whorls of flowers; leaves somewhat truncately broadly heart-shaped, obtuse (2--8' broad), long-petioled; flowers 6--9" broad; _stamens about 21; styles shorter than the ovary; achenes short-beaked_, the keeled back denticulate.--Swamps, Ill. to N. C. and Fla., west to Mo. and Tex.

ORDER 126. NAIADaCEae. (PONDWEED FAMILY.)

_Marsh or mostly immersed aquatic herbs, with stems jointed and leafy or_ (in Triglochin) _naked and scape-like, leaves sheathing at base or stipulate, and flowers perfect or unis.e.xual, often spathaceous, with perianth of 4 or 6 herbaceous distinct valvate segments, or membranous and tubular or cup-shaped, or none._ Stamens 1, 2, 4 or 6, with extrorse anthers. Ovaries 1--6, distinct or more or less coherent, 1-celled, usually 1-ovuled, in fruit follicular or capsular or an indehiscent berry or utricle.

SUBORDER I. Juncagineae. Marsh plants, with terete bladeless leaves; flowers perfect, spicate or racemose, with herbaceous 6- (rarely 3-) lobed perianth; carpels 3 or 6, more or less united, separating at maturity. Seeds anatropous; embryo straight.

1. Triglochin. Ovaries 3--6, united until maturity. Leaves radical.

Flowers bractless, in a spike-like raceme terminating a jointless scape.

2. Scheuchzeria. Ovaries 3, nearly distinct, at length divergent.

Flowers bracteate in a loose raceme upon a leafy stem.

SUBORDER II. Naiadeae. Immersed aquatics, with flat leaves; ovaries solitary or distinct, 1-ovuled.

[+] Flowers perfect, spiked or cl.u.s.tered; anthers 4 or 2, sessile; leaves alternate.

3. Potamogeton. Spike peduncled. Sepals 4, herbaceous. Anthers 4.

Ovaries 4, sessile.

4. Ruppia. Flowers on an enclosed spadix, at length long-exserted, without perianth. Anther-cells 4, distinct. Ovaries 4, becoming stipitate.

[+][+] Flowers moncious or dicious, axillary, naked, monandrous; leaves opposite (alternate in n. 6).

5. Zannich.e.l.lia. Moncious. Pistils (2--5) from a cup-shaped involucre or sheath.

6. Zostera. Pistils and stamens alternate in 2 vertical rows on the inner side of a leaf-like enclosed spadix. Stigmas 2, linear. Stem creeping.

7. Naias. Dicious; pistil solitary, naked. Stamen enclosed in a membranous spathe. Stems floating, with opposite or ternate leaves.

1. TRIGLCHIN, L. ARROW-GRa.s.s.

Sepals and petals nearly alike (greenish), ovate, concave, deciduous.

Stamens 3--6; anthers oval, on very short filaments. Pistils united into a 3--6-celled compound ovary; stigmas sessile; ovules solitary. Capsule splitting when ripe into 3--6 carpels, which separate from a persistent central axis.--Perennials, with rush-like, fleshy leaves, below sheathing the base of the wand-like naked and jointless scape. Flowers small, in a spiked raceme, bractless. (Name composed of t?e??, _three_, and ??????, _point_, from the three points of the ripe fruit in n. 1 when dehiscent.)

[*] _Fruit of 3 carpels._

1. T. pal.u.s.tris, L. Scape (6--18' high) and leaves slender; _sepals and stamens 6; fruit linear-club-shaped; carpels_ when ripe separating from below upward, leaving a triangular axis, _awl-pointed at base_.--Marshes, western N. Y. to Ill., Minn., and westward. Aug. (Eu., Asia, etc.)

2. T. striata, Ruiz & Pav. Scape (6--12' high) and leaves slender; flowers very small; _sepals and stamens 3; fruit globose-triangular_, or when dry 3-lobed. (T. triandra, _Michx._)--Sea-sh.o.r.e, Md. to Fla.

(S. Am., etc.)

[*][*] _Fruit of 6 carpels (rarely 5)._

3. T. maritima, L. Scape (1--3 high) and leaves thickish, fleshy; fruit ovate or oblong, acutish; carpels rounded at base and slightly grooved on the back, the edges acute.--Salt-marshes along the coast, Lab. to N. J., and in saline places in the interior across the continent. (Eu., Asia, etc.)

2. SCHEUCHZeRIA, L.

Sepals and petals oblong, spreading, nearly alike (greenish-yellow), but the latter narrower, persistent. Stamens 6; anthers linear. Ovaries 3, globular, slightly united at base, 2--3 ovuled, bearing flat sessile stigmas, in fruit forming 3 diverging and inflated 1--2 seeded pods, opening along the inside.--A low bog-herb, with a creeping jointed rootstock, tapering into the ascending simple stem, which is zigzag, partly sheathed by the bases of the gra.s.s-like conduplicate leaves, and terminated by a loose raceme of a few flowers, with sheathing bracts; leaves tubular at the apex. (Named for _John_ and _John Jacob Scheuchzer_, distinguished Swiss botanists early in the 18th century.)

1. S. pal.u.s.tris, L.--Peat-bogs, N. Brunswick to N. J., westward across the continent. June. (Eu., Asia.)

3. POTAMOGeTON, Tourn. PONDWEED.

Flowers perfect. Sepals 4, rounded, valvate in the bud. Stamens 4, opposite the sepals; anthers nearly sessile, 2-celled. Ovaries 4 (rarely only one), with an ascending campylotropous ovule; stigma sessile or on a short style. Fruit drupe-like when fresh, more or less compressed; endocarp (_nutlet_) crustaceous. Embryo hooked, annular, or cochleate, the radicular end pointing downward.--Herbs of fresh, or one in brackish, ponds and streams, with jointed mostly rooting stems, and 2-ranked leaves, which are usually alternate or imperfectly opposite; the submersed ones pellucid, the floating ones often dilated and of a firmer texture. Stipules membranous, more or less united and sheathing.

Spikes sheathed by the stipules in the bud, mostly raised on a peduncle to the surface of the water. (An ancient name, composed of p?ta??, _a river_, and ?e?t??, _a neighbor_, from the place of growth.)--By _fruit_, the full-grown fresh or macerated fruit is intended; by _nutlet_, that with the fleshy outer portion or epicarp removed. All except n. 19 flower in summer; the month mentioned indicates the time of ripening of the fruit.

-- 1. _Leaves of two sorts; floating ones more or less coriaceous, with a dilated petioled blade, different in form from the thinner submersed ones._

[*] _Submersed leaves reduced to narrowly gra.s.s-like or filiform sessile phyllodia._

[+] _Stems rather stout; stipules free; spikes all emersed, cylindrical and densely fruited; fruits fleshy and turgid, obliquely obovate._

1. P. natans, L. _Stem simple or sparingly branched_; floating leaves all long-petioled, elliptical or ovate, somewhat cordate at base, obtuse but with a blunt point, 21--29-nerved; upper submersed leaves lanceolate, early perishing, the lower (later in the season) very slender (3--7' long, barely 1" wide); upper _stipules very long, acute; peduncle about the thickness of the stem_; spikes 1--2' long; sides of the turgid _nutlet with a small deep impression in the middle_; embryo coiled into an incomplete elliptical ring.--Ponds and ditches, N. Scotia to Va., westward across the continent. In deeper or flowing water the plant becomes more slender and often wholly submersed (var. PROLiXUS, _Koch_).--Aug., Sept. (Eu., Asia.)

2. P. Oakesia.n.u.s, Robbins. Stem more slender, _much branched_; floating leaves smaller (1--1' long), ovate- or oblong-elliptical, obtuse, fewer-(17--23-) nerved; lowest submersed ones almost capillary (only --" wide), continuing through the flowering season; spikes shorter (--1' long), on _peduncles much thicker than the stem_; fruit smaller and more acute; _sides of the turgid nutlet not at all impressed_; curvature of the embryo nearly circular, its apex directed to a point above its base.--Ponds, and especially pools and stagnant ditches, Ma.s.s.

to N. J.; also Anticosti. Aug.

3. P. Pennsylvanicus, Cham. _Stems compressed_, often simple from the creeping rootstocks; floating leaves chiefly opposite (1--3' long), 11--17-nerved, oblong, tapering into a _short petiole_, the lower gradually narrowing and pa.s.sing into the submersed ones, which are very numerous and approximate, 2-ranked, linear (2--5' long, and 1--2"

wide), 5--7-nerved, the lateral nerves slender and nearly marginal, the s.p.a.ce within the inner nerves _coa.r.s.ely cellular-reticulated; stipules very obtuse_; spikes numerous, about the length of the thickened peduncle; _fruit round-obovate_, flattish, 3-keeled when dry; _nutlet distinctly impressed on the sides_; curvature of the embryo transversely oval. (P. Claytonii, _Tuckerm._)--Still or flowing water, N. Brunswick to S. C., west to N. Ind. and Minn. July, Aug.

[+][+] _Like the preceding section, but all the parts small, slender and delicate, only the fertile plants producing floating leaves; spikes very small and few-flowered; propagated by autumn buds._

4. P. Vaseyi, Robbins. Very delicate; stem almost capillary; _floating leaves obovate_ (3--5" long) and about the length of their filiform petioles, with 5 nerves deeply impressed beneath, cross-veins distinct; submersed leaves filiform-linear, very attenuate (1--2' long, {1/8}--"

wide) and acute; _stipules_ not adnate, scarious, _long_, acute; spikes all emersed, few, interrupted-oblong, 3--5-flowered, on a thickish peduncle; fruit oblique, round-obovate ({2/3}" long), compressed, slightly sharp-margined, tipped with a distinct recurved style, the sides impressed and face acute; upper portion of the embryo circularly incurved, its apex transverse to the fruit.--Canada and N. Eng.; also Ill. The fruiting form, with floating leaves, rare; the submerged form apparently much more abundant.

5. P. lateralis, Morong. Stem filiform, branching; _floating leaves elliptical_ (4--6" long by 2" wide), with 5--7 nerves deeply impressed beneath, tapering at base into a somewhat dilated petiole shorter than the blade; _submersed leaves linear_, acute (1--3' long by --" wide), 1--3-nerved, the mid-nerve with fine veins or cellular reticulations on each side, bi-glandular at base; _stipules short; peduncles with a very peculiar lateral appearance_, widely spreading at maturity, sometimes even recurved, often thicker than the stem; spikes often interrupted (2--4-flowered); fruit obliquely obovate (hardly 1" long), the back much curved, with two fine grooves upon it; embryo oval in its curve, the apex nearly touching the base.--Ma.s.s. and Mich.; rare. Undeveloped specimens resemble P. pusillus.

[+][+][+] _Stems slender or filiform, much branched; floating leaves sometimes wanting; stipules adnate to the base of the leaf; spikes of two kinds, one emersed, cylindrical and many-flowered, on a club-shaped peduncle, the other submersed, globular and few-flowered; fruit flat, cochleate, with thin or scarcely any flesh and a thin nutlet; embryo spiral._

6. P. Spirillus, Tuckerm. Floating leaves oval to lance-oblong and lanceolate (the largest 10" long, 4" wide), usually obtuse, about equalling the _rather dilated petioles_, with 5--many nerves beneath deeply impressed; upper submersed leaves either with or without a lance-oblong or broad-linear proper blade; the numerous lower ones narrow-linear, tapering toward the obtuse apex (--1' long, --{2/3}"

wide); stipules early lacerate; _submersed flowers usually solitary on very short erect peduncles; fruit_ with the back either _winged and with 4--5 distinct teeth or wingless and entire; embryo coiled 1 turns_.--Rivers, and even far up small streams, N. Eng. to Va., west to Mich. and Mo. June--Aug.--Stem less slender than in the next.

7. P. hbridus, Michx. Floating leaves oval to lance-oblong (the largest 10" long, 6" wide), often acute, longer than the _filiform petioles_, with about 5--7 nerves beneath deeply impressed; submersed leaves very numerous, almost setaceous (1--3' long, very rarely " wide); stipules obtuse; emersed spikes 4--7" long; _submersed_ spikes 1--4-flowered, their _peduncles_ (of their own length) _frequently recurved; fruit minute, about 8-toothed on the margin; embryo coiled 1 turns_.--Shallow stagnant waters, N. Brunswick to Fla., west to Mich., Mo., and N. Mex.

June--Aug.

[*][*] _Submersed leaves lanceolate, rarely oval or linear, membranaceous; spikes dense, many-flowered, on stout peduncles._

8. P. rufescens, Schrad. Stem simple; floating leaves (often wanting) 2--5' long, rather thin, _wedge-oblanceolate, narrowed into a short petiole_, 11--17-nerved; _submersed leaves almost sessile_, lanceolate and lance-oblong, smooth on the margin, fewer-nerved; stipules broad, hyaline, obtuse, upper ones ac.u.minate; spike 1--2' long, often somewhat compound; fruit obovate, lenticular, pitted when immature, with an acute margin and pointed with the rather long style; embryo incompletely annular.--In streams or ponds, N. Brunswick to N. J., west to Minn. and Tex. Aug., Sept. (Eu.)