GENUS i. 



FROG'S-BIT FAMILY. 



107 



i. LIMNOBIUM L. C. Richard, Mem. Inst. Paris, 32: 66. pi. 8. 1811. 



Aquatic, stoloniferous herbs, the leaves fascicled at the nodes, petioled, broad, cordate. 

 Flowers monoecious, white, arising from sessile or stipitate, 2-leaved, membranous spathes. 

 Perianth 6-parted ; segments petaloid, the 3 outer oblong to oval, the 3 inner oblong to linear. 

 Staminate flowers 2-4 in a spathe, long-penduncled, the stamens united in a column bearing 

 6-12 anthers at different heights, sometimes producing only 9-12 staminodia, the filaments 

 tipped with abortive anthers. Pistillate flowers sessile or short-peduncled with 3-6 vesti- 

 gial stamens ; ovary 6-9-celled with as many central placentae ; stigmas as many as the 

 cells, each 2-parted. Fruit a many-seeded berry. [Greek referring to the aquatic habitat.] 



Species, 3 or 4, natives of America. Type species : L. 

 Bosci L. C. Richard, the same as the following. 



i. Limnobium Spongia (Bosc.) L. C. Richard. 

 Frog's-bit. Fig. 253. 



Hydrocharis cordifolia Nutt. Gen. 2: 241. 1818. 



H. Spongia Bosc, Ann. Mus. Paris, 9: 396, pi. 30. 1807. 



Limnobium Spongia L. C. Richard, Mem. Inst. Paris, 32: 



66. pi. 8. 1811. 

 Limnocharis Spongia L. C. Richard ; Steud. Nomencl. Ed. 



2, Part 2, 45. 1841. 



Blades of the leaves orbicular or broadly ovate, cor- 

 date or reniform, faintly 5~7-nerved and cross-veined, 

 purplish and spongy beneath, io"-2' broad, on peti- 

 oles i'-io' in length. Stolons rooting and sending 

 up flowers and leaves at the nodes; peduncles of the 

 staminate flowers 3' -4' long, those of the pistillate 

 flowers stouter, \'-2.' long, nodding in fruit. 



In shallow, stagnant water, Lake Ontario, to Florida, 

 west to Illinois, Missouri and Texas. July-Aug. 



Family 10. GRAMINEAE Juss. Gen. 28. 1789.* 



GRASS FAMILY. 



Annual or perennial herbs, of various habit, rarely shrubs or trees. .Culms 

 (stems) generally hollow, but occasionally solid, the nodes closed. Leaves 

 sheathing, the sheaths usually split to the base on the side opposite the blade; a 

 scarious or cartilaginous ring, naked or hairy, rarely wanting, called the ligule, 

 is borne at the orifice of the sheath. Inflorescence spicate, racemose or panicu- 

 late, consisting of spikelets composed of two to many 2-ranked imbricated bracts, 

 called scales (glumes), the two lowest in the complete spikelet always empty, one 

 or both of these sometimes wanting. One or more of the upper scales, except 

 sometimes the terminal ones, contains in the axil a flower, which is usually enclosed 

 by a bract-like awnless organ called the palet, placed opposite the scale and with 

 its back toward the axis (rachilla) of the spikelet, generally 2-keeled ; sometimes 

 the palet is present without the flower, and vice versa. Flowers perfect, pistillate, 

 or staminate, sometimes monoecious or dioecious, subtended by 13 minute hyaline 

 scales called the lodicules. Stamens 1-6, usually 3. Anthers 2-celled, versatile. 

 Ovary i-celled, i-ovuled. Styles 1-3, commonly 2 and lateral. Stigmas hairy or 

 plumose. Fruit a seed-like grain (caryopsis). Endosperm starchy. 



About 4500 species, widely distributed throughout the world, growing in water and on all 

 kinds of soil. Those yielding food-grains are called cereals. The species are more numerous 

 in tropical countries, while the number of individuals is much greater in temperate regions, often 

 forming extended areas of turf. The time of year noted is that of ripening seed. 



A. Spikelets articulated below the empty scales or a subtending involucre, or attached to and 

 deciduous with the internodes of a readily disarticulating rachis, i -flowered, or if 2-flowered 

 the lower imperfect, usually staminate : rachilla not extending beyond the uppermost scale. 

 Spikelets round or dorsally compressed ; hilum punctiform. 



Fruiting scale and palet hyaline, thin, much more delicate in structure than the thick-mem- 

 branous to coriaceous empty scales. 



Spikelets unisexual, the pistillate borne in the lower, the staminate in the upper, part of 



the same spike. I. MAYDEAE. 



Spikelets in pairs, one sessile, perfect, the other pedicellate, perfect, staminate or empty, 



sometimes reduced to a single scale or wanting. II. ANDROPOGONEAE. 



Fruiting scale and palet never hyaline and thin, as firm as the empty scales, or firmer. 



Fruiting scale and palet membranous ; spikelets naked, spiny (in ours). III. ZOYSIEAE. 



* Text contributed by MR. GEORGE V. NASH. 



