Part 176 (1/2)

Flowers produced from a cleft in the margin of the frond, usually three together surrounded by a spathe; two of them staminate, consisting of a stamen only; the other pistillate, of a simple pistil; the whole therefore imitating a single diandrous flower. _Ster. Fl._ Filament slender; anther 2-celled, didymous; the cells dehiscent transversely; pollen-grains large, spherical, muricate. _Fert. Fl._ Ovary 1-celled; style and truncate or funnel-shaped stigma simple. Ovules and seeds 1--7.--Fronds 1--5-nerved, producing a single rootlet beneath (which is dest.i.tute of vascular tissue), proliferous from a cleft in the margin toward the base, and at length stipitate; the tissue abounding with bundles of rhaphides. (An old Greek name of uncertain meaning.)

[*] _Ovule solitary, orthotropous or nearly so; frond 1--3-nerved, thin._

[+] _Fronds oblong, stalked at base, remaining connected._

1. L. trisulca, L. Fronds oblong to oblong-lanceolate (6--9” long), attenuate at base into a slender stalk, denticulate at the tip, very obscurely 3-nerved, often without rootlets, usually several series of offshoots remaining connected; spathe sac-like; seeds ovate, amphitropous, with small round operculum.--Ponds and springy places, N. Scotia to N. J., west to the Pacific. (Eu.)

[+][+] _Fronds oblong to elliptical or round-ovate, sessile, soon separating._

2. L. Valdiviana, Philippi. _Fronds elliptic-oblong_, small (about 1”

long), rather thick, usually somewhat falcate, _obscurely 1-nerved; spathe broad-reniform_; utricle long-ovate, pointed by the long style; _seed orthotropous_, oblong, _with a prominent acute operculum_. (L.

Torreyi, _Austin._)--Pools, N. J. and southward, westward across the continent. (S. Am.)

3. L. perpusilla, Torr. _Fronds obovate or roundish-obovate_, oblique (1--1” long), _obscurely 3-nerved_; utricle ovate; style rather long; _seed orthotropous_, ovate or oval, obtuse, _with scarcely apiculate operculum_.--N. Y. and N. J., west to Mich. and Wisc.--Var. TRINeRVIS, Austin, has larger, distinctly 3-nerved fronds, and an unequally cordate seed.

4. L. mnor, L. _Fronds round- to elliptic-obovate_ (1--2” in diameter), rather thick, _very obscurely 3-nerved; spathe sac-like_; utricle short-urn-shaped, tipped with a short style; seed oblong-obovate, _amphitropous, with prominent rounded operculum_.--Stagnant waters, throughout N. Am. (Eu.)

[*][*] _Ovules 2--7, anatropous; fronds very thick and spongy, flat above, very obscurely 5-nerved (1--3” long)._

5. L. gibba, L. Fronds obovate-elliptic to nearly orbicular, almost hemispherical, soon separating; bract sac-like.--Mo. (?) to Ariz. and Calif.

3. WoLFFIA, Horkel.

Flowers central, bursting through the upper surface of the globular (or in some foreign ones flat) and loosely cellular frond, only 2; one consisting of a single stamen with a 1-celled 2-valved anther; the other of a globular ovary, tipped with a very short style and a depressed stigma. Ovule orthotropous, rather oblique in the cell. Utricle spherical. Alb.u.men thin.--Fronds rootless, proliferous from a cleft or funnel-shaped opening at the base, the offspring soon detached; no rhaphides.--The simplest and smallest of flowering plants, from --{2/3}” long (an African and Cuban species much larger), floating as little grains on the water. (Named for _John Fred. Wolff_, who wrote on Lemna in 1801.)

1. W. Columbiana, Karsten. Globose or globular, {1/3}--{2/3}” long, very loosely cellular, light green all over, not dotted; stomata 1--6; the opening at the base circular and with a thin border.--Floating rather beneath the surface of stagnant waters, Conn. to N. J., west to Minn. and La.

2. W. Brasiliensis, Weddell. Oblong, smaller and more densely cellular, flattish and deep green with many stomata above, tumid and pale below, brown-dotted all over, anterior edge sharp, opening at base circular.--Growing with the last, but floating on the surface.

ORDER 125. ALISMaCEae. (WATER-PLANTAIN FAMILY.)

_Marsh herbs, with scape-like stems, sheathing leaves, and perfect or moncious or dicious flowers; perianth of 3 herbaceous persistent sepals and as many (often conspicuous) white deciduous petals, which are imbricate or involute in bud; stamens 6 or more, included; ovaries numerous, distinct, 1-celled and mostly 1-ovuled, becoming achenes in fruit_ (in our genera); _seeds erect; campylotropous._--Roots fibrous; leaves radical, petiolate and strongly nerved with transverse veinlets, the earlier sometimes without blade; flowers long-pedicellate, mostly verticillate, in a loose raceme or panicle, with lanceolate scarious bracts slightly connate at base.

1. Alisma. Flowers perfect, usually 6-androus. Carpels flattened, in one whorl.

2. Sagittaria. Flowers mostly unis.e.xual. Stamens rarely few. Carpels flattened, in dense heads, winged.

3. Echinodorus. Flowers perfect. Stamens 6 or more. Carpels capitate, turgid and ribbed, often beaked.

1. ALiSMA, L. WATER-PLANTAIN.

Flowers perfect. Petals involute in the bud. Stamens definite, mostly 6.

Ovaries many in a simple circle on a flattened receptacle, forming flattened coriaceous achenes, which are dilated and 2--3-keeled on the back.--Roots fibrous. Leaves all from the root, several-ribbed, with connected veinlets. Scape with whorled panicled branches. Flowers small, white or pale rose-color. (The Greek name; of uncertain derivation.)

1. A. Plantago, L. Perennial by a stout proliferous corm; leaves long-petioled, ovate, oblong, or lanceolate or even linear, acute, mostly rounded or heart shaped at base, 3--9-nerved; panicle loose, compound, many-flowered (1--2 long); carpels obliquely obovate, forming an obtusely triangular whorl in fruit.--Shallow water and ditches, across the continent. Very variable as to foliage, but the leaves usually more broadly cordate-ovate than in Old World forms (var.

Americanum, _R. & S._); when growing under water thinner and narrowly lanceolate. (Eu., etc.)

2. SAGITTaRIA, L. ARROW-HEAD.

Flowers moncious, or often dicious in n. 1 and 4, and polygamous in n. 7. Petals imbricated in the bud. Stamens indefinite, rarely few.