44 NORTH AMERICAN FLORA [VorLumME 17 
length, usually slender, sometimes. filiform ; bracts lanceolate or linear, often acuminate ; 
sepals broadly ovate to suborbicular, obtuse; petals white or pinkish, 1-2 mm. long; 
achene-heads 3.5-4.5 mm. broad, the achenes obliquely obovate, 1.5-2 mm. long, the beak 
small, ascending. 
TYPE LOCALITY : United States. 
DISTRIBUTION: Massachusetts to Minnesota, Florida, and Texas. 
ILLUSTRATION : Britt. & Brown, Ill. FL. /f. 188. 
2. Alisma brevipes Greene, Pittonia 4: 158. 1900. 
Alisma superbum Tunell, Bull. Leeds Herb. 2: 5. 1908. 
Plants similar to those of 4. subcordatum in habit, but commonly larger ; leaf-blades 
oblong or oblong-lanceolate to ovate, 5-19 cm. long, acute, sometimes abruptly pointed at 
the apex, rounded, truncate or subcordate at the base or sometimes gradually narrowed to 
the petiole, which commonly exceeds the blade in length; scapes 1 m. tall or less, the 
branches and pedicels very numerous, except in small plants; bracts lanceolate or linear- 
lanceolate ; sepals suborbicular: or orbicular-ovate, mostly over 3 mm. long; petals white, 
5-6 mm. long; achene-heads 5-6.5 mm. broad, the achenes obovate, 2.5-3 mm. long, the 
beak ascending. 
TYPE LOCALITY : Piedra, Colorado. 
DISTRIBUTION: Nova Scotia to British Columbia, North Dakota, and California. 
3. Alisma Geyeri Torr. in Nicollet, Rep. Hydrograph. 
Miss. Riv. 162. 1843. 
Alisma validum Greene, Pittonia3: 156. 1896, 
Alisma arcuatum Lunell, Bot. Gaz. 43: 210. 1907. Not A. arcuatum Michalet. 1854. 
ere pumilum Lunell, Bot. Gaz. 43: 211. 1907. Not A. arcuatum pumilum Prahl. 
Alisma arcuatum lanceolatum Lunell, Bot. Gaz. 43: 211. 1907. Not A. lanceolatum With. 1796. 
Alisma arcuatum angustissimum Lunell, Bot. Gaz. 43: 211. 1907. Not A. Plantago angustis- 
simum DC, 1815. 
Plants diffuse; leaf-blades oblong, elliptic, oblong-lanceolate or ovate-lanceolate, or 
rarely linear, 5-9 cm. long, acute or slightly acuminate at the apex, narrowed at the 
base; the petioles usually longer than the blades; scapes mostly 1-5 dm. long, more or 
less diffusely spreading, the branches and pedicels relatively stout; bracts lanceolate; sepals 
orbicular-ovate, about 2.5mm. long; petals pink, 24 mm. long; achene-heads 4.5-5.5 mm. 
broad, the achenes suborbicular, about 2 mm. in diameter, the beak erect or nearly so. 
TYPE LOCALITY: Near Devils Lake, North Dakota. 
DISTRIBUTION : Western New York to North Dakota, Oregon, and Nevada. 
2. MACHAEROCARPUS Small, gen. nov. 
Perennial scapose herbs. Leaves erect, ascending or floating; blades dilated, 3-5- 
veined, not lobed at the base, long-petioled. Flowers perfect, borne in simple panicles. 
Sepals 3, broad, ribbed, persistent. Petals 3, white or pink, spreading, incised, deciduous. 
Stamens 6, two opposite each sepal; filaments flattened; anthers elongate. Carpels few, 
in one whorl, attached to the conic receptacle by their broad bases. Achenes in one radiant 
whorl, ribbed on the back, the faces depressed, the beak erect, as long as the achene-body 
or longer. 
Type species, Damasonium californicum Torr. 
1. Machaerocarpus californicus (Torr. ) Small. 
Damasonium californicum Torr.; Benth. Pl. Hartw. 341. 1857. 
Alisma californicum Micheli, in DC. Monogr. Phan. 3: 34. 1881. 
Leaf-blades oblong to ovate or linear-oblong, 2.5-6 cm. long, obtuse at the apex, obtuse, 
rounded, truncate, or subcordate at the base, the petioles, at least some of them, much 
longer than the blades; scapes usually several together, erect or decumbent, 14 dm. long, 
the pedicels loosely spreading or recurving at least in fruit; sepals broadly oblong or ovate- 
