LEMNACEAE 229 
fluent at maturity. Ovary 3-4-celled, oblong. Ovules 2-8, anatropous. Fruits gelatinous, 
2-3-celled. Seeds several. Endosperm copious. CALAMUS. SWEET FLAG. 
1. Acorus Calamus L. Rootstocks horizontal, pungent-aromatic: leaves several 
5-20 dm. tall; blades linear, attenuate, sharp-edged, bright green : scape quite similar to 
the leaves, often narrower: spathe similar to the leaves, extending 2-8 dm. beyond the 
spadix, attenuate, erect: spadix elongated-conic, 3-8 cm. long, yellowish, ascending or 
spreading, densely flowered : fruits 4-5 mm. long, lustrous. 
In marshes and springy places, Nova Scotia to Minnesota, Floridaand Texas. Spring and summer. 
FAMILY 2. LEMNACEAE Dumort. DUCKWEED FAMILY. 
Perennial floating herbs, consisting chiefly of very small, often minute, fleshy 
structures, representing modified stems, sometimes with 1 or several roots. 
Vegetative reproduction is accomplished by lateral branching. Propagative 
pouches 1 or 2 in each body. Flowers monoecious, one or two staminate and 
one pistillate, arising from a point in a propagative pouch. Staminate flowers 
consist of1lstamen.  Anthers 1-2-celled : sacs opening length wise or transversely. 
Pollen of minutely barbellate spherical grains.  Pistillate flowers consist of 1 car- 
pel, stigmatic at the apex. Ovules one or several. Fruit a utricle. 
Plant-body much elongated or subglobose, not disk-like, rootless: propagative pouch solitary. 
Plant-body very thick or subglobose. 1. WOLFFIA. 
Plant-body thin, tongue-like or saber-form. 2, WOLFFIELLA. 
Plant-body disk-like, with 1 root or several roots: propagative pouches 2. 
Plant-body inconspicuously nerved : root solitary, without a fibro-vascular bundle. 3. LEMNA. 
Plant-body conspicuously nerved : roots several, each with a fibro-vascular bundle. 4. SPIRODELA. 
1. WOLFFIA Horkel. 
Plant-body much thickened or subglobose, with the stipe attached beneath the propa- 
gative pouch near the margin. Propagative pouch funnelform, opening near the base of 
the plant-body. Spadix of 1 staminate and 1 pistillate flower bursting through the upper 
surface of the plant-body. Anther l-celled. Ovule 1, orthotropous. Utricle smooth. 
Plant-body smooth, somewhat flattened above, gibbous beneath, brown-punctate. 1. W. punctata. 
Plant-body ellipsoidal or globose, with 2-3 papules on dorsal surface, not punctate. 2. W. Columbiana. 
1. Wolffia punctata Griseb. Plants solitary ; body boat-like, elliptic to ovoid-ob- 
long, 0.58-0.82 mm. long, flat, or nearly so above, gradually rising at the apex, whole 
surface punctate with brown cells: tissue various; lower portion of the plant-body com- 
posed of larger cells than the upper. [ W. Brasiliensis fof Am. Auth., not of Wedd. ] 
In still or stagnant water, Ontario to Michigan, Illinois and Tennessee. Summer. 
2. Wolffia Columbiana Karst. Plants solitary ; body globose to ellipsoidal, 0.48- 
1 mm. long, the upper surface convex, with a row of inconspicuous papillae only a small 
portion emersed, this with 1-10 stomata, not punctate: tissue of uniform large cells. 
In lakes and pools, Massachusetts to Ontario, Minnesota, Florida and Louisiana. Spring to fall. 
2. WOLFFIBLLA Hegelmaier. 
Plant-body thin, tongue-shaped or saber-form, with the stipe attached on the margin of 
the propagative pouch. Roots wanting. Propagative pouch solitary, triangular, opening 
by a slit in the basal margin of the plant-body. Inflorescence and fruit unknown. 
1. Wolffiella Floridàna (J. D. Smith) C. H. Thompson. Plants minute, solitary or 
usually several generations cohering, thus forming dense mats ; body elongated, attenuate 
from the base to the slender apex, 5.5-8.5 mm. long, hollow except near the apex. 
In still or stagnant water, Missouri to North Carolina, Georgia, Florida and Texas. Spring to fall. 
3. LEMNA L. 
Plant-body disk-like, with 1-5 inconspicuous nerves, the stipe attached to the basal mar- 
gin. Roots solitary, each with a blunt or pointed root-sheath. Propagative pouches 2, 
triangular, opening by slits in either margin of the basal part of the thallus. Spadix of 
1 pistillate and 2 staminate flowers, arising’ from the propagative pouches. Anthers 2- 
celled : sacs opening transversely. Ovary with 1 orthotropous and amphitropous ovule or 
2-6 anatropous ovules. Utricle somewhat flattened, often ribbed. DUCKWEED. 
Plant-bodies long-stipitate, forming large submerged masses. 1. L. trisulca.. 
Plant-bodies sessile, or short-stipitate, floating, more or less detached. 
Plant-body symmetrical or nearly so. k 
Plant-body oblong-obovate : utricle lenticular. 2. L. minor. 
