48 POACEAE 
FAMILY 2. HYDROCHARITACEAE Aschers. FRoG's-BIT FAMILY. 
Aquatic or mud-inhabiting herbs. Leaves clustered, usually with well de- 
veloped blades. Flowers monoecious or dioecious, arising from spathes of distinct 
or united bracts. Perianth regular, superior, of 3 sepals and 3 petals. Androe- 
cium of 6-12 stamens. Filaments distinct or partially united. Gynoecium of 
6-15 united carpels. Ovary inferior, usually 6-9-celled. Styles as many as the 
cavities of the ovary. Ovules numerous. Fruit usually indehiscent. 
Leaf not differentiated into blade and petiole: flowers dioecious: stamens distinct: anthers nearly 
sessile. _ ; : : ; 1. THALASSIA. 
Leaf differentiated into blade and petiole: flowers monoecious : stamens with united 
filaments. 2. LIMNOBIUM. 
l. THALASSIA Banks. 
Marine herbs, with elongated rootstocks. Leavesseveralata joint, sheathing at the base: 
blades linear, elongated. Scape arising from the cluster of leaves. Flowers dioecious, solitary 
in narrow spathes of two bracts : these united into a tube at the base. Staminate flowers long- 
pedicelled : perianth of 3 petaloid sepals: stamens 6: filaments very short: anthers open- 
ing laterally. Pistillate flower nearly sessile in the spathe, caducous : ovary 6-9-celled, 
beaked. Fruit stalked, rugose or nearly echinate, opening by many valves. Seeds numerous. 
1. Thalassia testudinum Koenig & Sims. Submersed, glabrous.  Rootstocks creep- 
ing, elongated : stems short, arising from the nodes of the rootstock : leaves 2-5, sheathing 
the stem ; blades linear, strap-like, 0.5-3 dm. long, obtuse, withering-persistent : scapes 
solitary, central: fruit globose or oval, echinate-pubescent, slightly pointed. 
In shallow water, along the coast of peninsular Florida. Also in the West Indies. 
2. LIMNÓBIUM L.C. Rich. 
Aquatic herbs usually floating and producing pendent roots and stolons. Leaves 
clustered : petioles elongated : blades broad, several-nerved. Flowers monoecious, from 
spathes of 2 membranous bracts. Perianth white: sepals 3: petals 3, narrower than the 
sepals, Staminate flowers 2—4 in a spathe, usually with 6-12 stamens : filaments united into 
a column, bearing the anthers at different heights. Pistillate flowers with 3-6 abortive 
stamens, a 6-9-celled ovary with several central placentae : stigmas as many as the cavities 
in the ovary, each 2-parted. Fruit a many-celled berry. 
1. Limnobium Spóngia (Bosc) L. C. Rich. Acaulescent, stoloniferous. Leaves 
basal ; petioles erect or ascending, 5-25 cm. long: blades ovate to suborbicular or reniform, 
2-5 em. broad, obtuse, entire, truncate or cordate at the base; petioles tapering to the 
blade : flowers monoecious ; staminate on scapes 8-10 cm. long ; pistillate on shorter and 
stouter scapes, these recurving at maturity: berry nodding, oval, 1-1.5 cm. long. 
In shallow water or mud, Ontario to Illinois and Missouri, to Florida and Louisiana. FROG'S-BIT. 
Order 5. POALES. 
Mostly perennial caulescent or acaulescent plants, commonly known as 
GRASSES and SEDGES. Stems (culms) simple or branched, sometimes conspicu- 
ously jointed. Leaves alternate, mostly sheathing at the base: blades usually 
narrow and elongated, entire or nearly so. Flowers variously disposed in à 
simple or compound inflorescence, perfect, or rarely monoecious or dioecious, 
incomplete, inconspicuous, in the axils of chaffy bracts or scales (glumes). 
Fruit a caryopis (grain) or an achene. 
Leaves 2-ranked, their sheaths with ununited margins: stems mostly hollow: fruit a grain (caryopsis). 
; ; Fam. 1. POACEAE. 
Leaves3-ranked, their sheaths with united margins: stems solid : fruitan achene. Fam. 2. CYPERACEAE. 
FAMILY 1. POACEAE R. Br! Grass FAMILY. 
Annual or perennial herbs, rarely shrubs or trees, sometimes monoecious or 
dioecious, varying much in habit. Stems (culms) usually hollow, the nodes 
closed. Leaves alternate, 2-ranked, sheathing, the sheaths generally open to 
the base on the side opposite to the blade; a scarious or cartilaginous ring 
1Contributed by Mr. George V. Nash. 
/ 
