26 Order POALES 
1. Spirodela. 232. 
1. Spirodela polyrhiza (L.) Schleid. Greater Duckweed. 
Common on the surface of ponds and slow streams. Anselmo; Fre- 
mont; Lincoln; Long Pine; Thedford; Valentine. 
2. Lemna. 232. 
Duckweeds. 
Thallus with a stalk-like projection at the base. 
Stalk long, thallus 5 to 15 mm, long. 1. L. trisulea. 
Stalk short, thallus less than 5 mm. long. 2. L. perpusilla. 
Thallus not stalked. 
Thallus nearly symmetrical, green or purplish beneath. 3. L. minor. 
Thallus unsymmetrical, pale beneath. 4. L. gibba. 
1. Lemna trisulca L. ‘ 
Common in ponds throughout the state. Ashland; Cherry county; 
Fremont; Greenwood; Harrison; Newark; Thedford. 
2. Lemna perpusilla Torr. 
Thomas county. 
3. Lemna minor L. 
Common on the surface of ponds or slow streams. Anselmo; Ban- 
ner county; Cherry county; Holt county; Long Pine; Pine Ridge; 
Valentine. 
4. Lemna gibba L. 
In ponds in the sand-hill regions. Kennedy; Merriman; Thomas 
county. 
3. Wolffia. 233. 
1. Wolffia punctata Griseb. 
In ponds, rare. Bellevue; Long Pine. 
POALES. (GRAMINALES.) 
Leaves 3-ranked, with closed sheaths; stems usually solid; fruit an 
achene, i. e. seed free from ovary wall. 1. Cyperacee. 
Leaves 2-ranked, with open sheaths; stems usually hollow; fruit a 
caryopsis or cereum, i. e. seed united to ovary walls. 2. Poacezx. 
1. CYPERACEZ. 
Sedge Family. 
The sedges closely resemble the grasses and are often confused with 
them. Most sedges prefer a moist soil, but a few are xerophytic. 
In low meadow lands they often furnish a large part of the forage, 
but are inferior to the true grasses for hay and pasture. 
Flowers of the spikelets all, or at least some of them, perfect; 
achene not in a perigynium. 
Perianth of scale-like sepals. 
Perianth of 3 scales and 3 bristles; stamens three. 1. Fuirena. 
Perianth of a single hyaline scale; no bristles; only one stamen. 
2. Hemicarpha. 
