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NEW YORK STATE MUSEUM 



(achenium) enclosed in a thin or membranous seed vessel (peri- 

 gynium), which is also in the axil of a scale-like bract ; both kinds 

 of flowers arranged in spikes which are staminate (sterile) when 

 composed of staminate flowers, pistillate (fertile) when composed 

 of pistillate flowers, and androgynous when composed of both 

 kinds. The spikes may be either sessile or borne on a peduncle, 

 and they are usually subtended by scale- like or foliaceous bracts. 

 When both kinds occur on the same plant the inflorescence is 

 monoecious, on different plants, dioecious. The stems or culms 

 are triangular and solid ; leaves three-ranked, narrow, linear or 

 setaceous, often rough on the margins, clasping the stem at the 

 base and forming a closed sheath around it. 



Perennial herbs growing chiefly in wet, moist or swampy 

 places, and most of them perfecting their fruit in the first 

 half of the summer season. They may be distinguished from 

 the true grasses by their triangular solid stems, their closed 

 sheaths and their seed being wholly and singly enclosed in a thin 

 seed vessel. 



For the sake of brevity the following characters have been 

 employed : 



The sign of degrees (°) stands for "foot" or "feet." 

 The sign of minutes (') stands for "inch" or "inches." 

 The sign of seconds (") stands for " line " or " lines." 

 The dash between two numbers stands for " to," and with the 

 numbers indicates the degree of variation in measurement. 



Synopsis of the Groups. 



A. Staminate and pistillate flowers in small globose or oblong 

 androgynous spikelets placed one above the other and forming 

 clusters or interrupted spikes or heads at the summit of the culm, 

 or panicled heads (decompound) in 3, 4 and 5. Sometimes the 

 lower spikelets in several species are branched. Androgynes. 



* Stigmas 2; achenium lenticular. 



f Spikelets staminate at the apex, pistillate below. 



Spikelets 2-5 flowered, capitate or in a short interrupted spike; 

 root-stock extensively creeping. 1-2. 



Spikelets in a close or open panicle or densely clustered in an 

 interrupted spike 1-4' long or more; perigynia blackish-brown or 

 tawny. 3-5. 



