66 



CONTRIBUTIONS FROM THE NATIONAL. HERBARIUM. 



15. VALIISNERIACEAE. Eel-grass Family. 



Plants with branching stems, without tubers; leaves ovate-oblong to linear, 0.5-2 

 cm. long, opposite or whorled; staminate flowers axillary, the sepals and petals 

 3 ; pistillate flowers with a 6-parted perianth and a long capillary tube . 



1. ANACHARIS. 



Plants stemless, stoloniferous, producing Monter tubers; leaves linear, grasslike, 

 5-nerved, 40-150 cm. long, 1-2 cm. wide; staminate flowers numerous on a conic 

 receptacle, inclosed in a spathe, the perianth 3-parted; pistillate flowers single 

 on a Icmg scape reacldng the surface of the water and coiling spirally during the 

 maturing of the fruit, the perianth 3-parted, the tube adherent to the ovary. 



2. VALLISNERIA. 



1. ANACHARIS L. Rich. 



1. Anacharis canadensis (Michx.) Babingt. 



Water-weed. 

 Abundant in the Potomac. June- July. 

 Eastern N . Amer. (Elodea canadensis Michx. ; 

 Philoiria canadensis Britton.) 



2. VALLISNERIA T.. 



1. Vallisneria spiralis L. 



Eel-grass. Wild celery. 

 Abundant in the Potomac and its tributa- 

 ries. July. Eastern states, south to N. C. 



16. POACEAE. Grass Family. 



The cultivated grains of the region are 

 often found growing spontaneously in waste 

 places, especially in the vicinity of freight 

 stations and along railways. These are 

 mentioned under their respective genera, 

 except corn or maize {Zea mays L.). The 

 commoner ornamental grasses are; eulalia, 

 Miscanthus sinensis Anderss.; plume-grass, 

 Cortaderia argentea (Nees) Stapf, a tall reed, 

 growing in large clumps, with numerous long 

 narrow drooping blades, a flower stalk 1^2 

 FIG. l-Tho inflorescence, spikelet, and floret of "^e^ers long, surmounted by a silvery white 

 a grass (i?ro7?iM« sfcoZinws). plume 30-60 cm. long; and two species of 



Pennisetum, GO-lOO cm. high, used as border 

 plants, P. villosura R. Br., with short broad heads and plumose bristles, and P. rupellii 

 Steud., the fountain grass, with slender rose-colored spikes tapering at the apex. 



The grass flower consists normally of a pistil and 3 stamens contained between 2 

 small bracts, these being aggregated in spikelets (Fig. 1). The spikelet ia made up 

 of a central axis {rachilla) upon which the bracts are arranged in 2 ranks. The lower- 

 most pair of bracts (ghcmes) are without flowers. The succeeding bracts (lemmas) 

 have flov\'ers and an inner bract (jmlea) next the rachilla. The lemma, palea, and 

 flower are together called the floret. If a lemma contains no flower it is called a sterile 

 lemma. The spikelets may be 1-flowered or several-flowered and are almost always 

 aggregate in an inflorescence. 



Spikelets with 1 perfect terminal floret (unisexual in Maydeae and in Zizania) and a 

 sterile or staminate floret below, usually represented by a sterile lemma only; 

 rachilla articulate below the glumes, the more or less dorsally compressed spikelets 



