INTRODUCTION. 



In order to make the present publication more useful 

 to students of grasses, the order Graininese and the sev- 

 eral tribes into which the order has been divided by our 

 best authorities are here briefly characterized. Under 

 the tribes the genera which are native or have been 

 introduced are enumerated, and those having species 

 figured in this bulletin are marked with an asterisk ( # ). 



GRAMINEiE— GRASSES. 



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

 herbaceous (rarely woody) plants, with usually hollow, cylindri- 

 cal (rarely flattened) and jointed stems (culms) whose internodes 

 for more or less of their length are 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, 

 which are arranged in panicles, racemes, or spikes, and which con- 

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

 distichous imbricated 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 (excepting 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 envelops the flower 

 by its infolded edges. At the base of the flower, between it and 

 its glume, are usually two very small hyaline scales (lodicules)', 



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