Parr 1, 1909] ALISMACEAE 45 
oblong, 4-5 mm. long; petals suborbicular, 8-10 mm. long; achenes dagger-like, 6-10, 
horizontally radiant, 7-12 mm. long, the beak subulate. 
TYPE LOCALITY: Sacramento, California. 
DISTRIBUTION: Northern California. 
ILLUSTRATIONS : Pacif. R. R. Rep. 4: £/. 21; Engler, Pflanzenreich 415: f. 9. 
3. HELIANTHIUM Engelm.; Britton, Man. ed. 2. 54. 1905. 
Annual or perennial, scapose, marsh or aquatic herbs. J,eaves erect or ascending, or 
floating ; blades narrow and gradually narrowed into thepetiole or broad and deeply cordate 
at the base, 3-several-ribbed. Scapes as long as the leaves or longer, terminating in a few- 
flowered whorl or a many-flowered panicle, the pedicels spreading or recurving in fruit. 
Flowers perfect. Sepals 3, broad, embracing the fruit-head or reflexed beneath it. Petals 
3, mainly white or pink, about as long as the sepals. Stamens 6 or 9; filaments elongate; 
anthers very short, often broader than long. Carpels relatively few, borne in few series on 
an elevated receptacle. Style not apical, minute; stigma acute. Achenes forming a 
globular or depressed head, turgid, crested-ribbed, obscurely beaked or beakless. 
Type species, Echinodorus parvulus Engelm. 
Leaf-blades narrow, acute at the base; inflorescence simple; sepals ate the fruit-head ; 
stamens 9. 1. A. parvulum. 
Leaf-blades broad, cordate at the base; inflorescence compound; sepals 
reflexed under the fruit- head ; stamens 6. 2. H. nymphaetfolium. 
1. Helianthium parvulum (Engelm.) Small. 
? Alisma tenellum Mart.; R. & S. Syst. Veg. 7: 1600. 1830. 
Echinodorus parvulus Engelm. in A. Gray, Man. ed. 2. 438. 1856. 
? Echinodorus tenellus Buch. Abh. Nat. Ver. Bremen 2: 18. 1868. 
Hlelianthium tenellum Britton, Man. ed. 2. 54. 1904. 
Plants 1.5 dm. tall or less; leaf-blades linear to elliptic or oblong, 1-3 cm. long, acute 
or acutish at the apex, 3-veined, gradually narrowed into the slender petioles which usually 
somewhat exceed the blade in length; scapes solitary or few together, mostly as long as 
the leaves or longer; pedicels mostly 2-8, recurved in fruit, 5-25 mm. long; sepals orbic- 
ular-ovate or deltoid-ovate, 1.5-2 mm. long; petals suborbicular, about as long as the 
sepals, emarginate at the apex; fruit-heads globular, 3-4 mm. in diameter, embraced by 
the persistent calyx; achenes 1-1.5 mm. long, the ribs obscurely crested. 
TYPE LOCALITY: Michigan. 
DISTRIBUTION : Massachusetts to western Ontario, Minnesota, Florida, and Texas; Mexico ; 
Cuba. Perhaps also in South America. 
ILLUSTRATIONS : Britt. & Brown, ii. Fl. f. 189 (excluding the flower and fruit) ; Rhodora 5: 
pl. 45, f. 1-10; A. Gray, Man. ed. 7. AB . 
2. Helianthium i aaplaeitelias (Griseb.) Small. 
Alisma nymphaeifolium Griseb. Cat. Pl. Cuba 218. 1866. 
Echinodorus nymphaeifolius Buch. Bot. Jahrb. 2: 483. 1882. 
Plants several dm. tall; leaf-blades ovate to oblong-ovate, 5-14 cm. long, rounded at 
the apex, 9-13-veined, deeply cordate at the base, the petioles stout, often greatly elongate ; 
scapes solitary or few together, the pyramidal panicle usually exceeding the leaves; pedi- 
cels numerous, becoming 9-22 mm. long; sepals ovate, usually broadly so, 1-1.5 mm. 
long; petals suborbicular, scarcely as long as the sepals, rounded at the apex; fruit-heads 
depressed, 4-5 mm. broad, subtended by the reflexed persistent calyx; achenes about 2 
mm. long, the ribs prominently crested. 
TYPE LOCALITY: Western Cuba. 
DISTRIBUTION : Cuba. 
4. ECHINODORUS Rich.; Engelm. in A. Gray, 
Man. 460. 1848. 
Annual or perennial, usually acaulescent, marsh herbs. Leaves erect or ascending ; 
blades sometimes ample, several-ribbed. Scapes usually surpassing the leaves, often greatly 
elongate, the flower-whorls usually remote, the pedicels very short or relatively short. 
Flowers perfect. Stamens 12-30, or rarely fewer; filaments often about as long as the 
