GRASSES OF IOWA. 



GRASSES— GRAMINEiE. 

 General Description. 



Characters of the Order. — Fibrous-rooted, annual or perennial, 

 herbaceous plants (among our species Arundinaria alone is 

 woody), with usually hollow, cylindrical (rarely flattened) and 

 jointed stems (culms) whose internodes for more or less of 

 their length are completely enveloped by the sheath-like basal 

 portion of the two-ranked and usually linear, parallel- veined 

 leaves. 



Flowers without any distinct perianth, hermaphrodite or 

 rarely unisexual, solitary or several together, in spikelets, 

 these disposed in panicles, racemes or spikes, and consisting 

 of a shortened axis (the rachilla) and two or more chaff- like, 

 distichous bracts (glumes), of which the first two, rarely one 

 or none or more than two, are empty (empty glumes); in the 

 axil of each of the succeeding bracts (except sometimes the 

 uppermost) is borne a flower (hence these are named flowering 

 glumes). Opposed to each flowering glume, with its back 

 turned toward the rachilla, is (usually) a two-nerved, two- 

 keeled bract or prophyllum (the palea), which frequently envel- 

 ops the flower by its enfolded edges. This bract is the pro- 

 phyllum of the extremely short axis or branch which supports 

 the flower; its absence indicates that the flower is strictly ses- 

 sile or inserted directly on the rachilla; the rachilla or axis of 

 the spikelet may or may not be produced beyond the palea. 

 At the base of the flower, between it and its glume, are usually 

 two very small hyaline scales (lodicules); rarely there is a 

 third lodicule between the flower and the palea. Stamens, 

 usually three (rarely two or one, or more than three), with very 

 slender filaments and two-celled, usually versatile anthers. 

 Pistil with a one-celled, one-ovuled ovary, and one to three, 

 usually two, styles, with variously-branched, most frequently 

 plumose, stigmas. Fruit, a true caryopsis, rich in albumen. 

 (In Sporobolus and Eleusine the fruit is a utricle, the seed 

 being loose within the thin pericarp.) Embryo small, lying at 

 the front and base of the seed, covered only by the thin pericarp. 



