66 Rhodora [April 



mens in the Gray Herbarium, clearly distinct from 6". lacustris L., 

 though reduced to synonymy in the Kew Index. To this form our 

 American S. validus and S. occidetitalis are more nearly allied than 

 to S. lacustris L. 



The achene-characters here given are based on study of mature 

 plants ; and achenes for measurement and illustration are in each 

 case takeh from the lower part of the spikelet, the upper achenes 

 being found less characteristic and almost invariably smaller than the 

 lower ones. 



Key to American Allies of Scirpus lacustris. 



Achene lenticular, style 2-cleft : 

 Bristles 4-6, slender: 



Achene 2 mm., scales but little longer . . 5'. validus. 



Achene 2.5-3 f""i-' scales \-l longer ... 6'. occidetitalis. 



Bristles 2, broad, ciliate below 5'. Cali/ornicus. 



Achene triquetrous, style 3-cleft ; bristles 2-4, fragile, 



unequal 5. hetcrocltaetus, 



SciRPUS VALIDUS Vahl Enum. PI. 2:268 (1806). 



Scirpus lacustris of American authors not Linnaeus. 



Perennial: rootstock horizontal: culm erect, 1.2-2.5 "^- high, 

 0.8-2.5 cm. in diameter at base, attenuate upward, terete, soft, usually 

 flattened in dried specimens, light green, smooth, minutely striate, 

 leafless, or the basal sheaths produced into narrow acuminate blades 

 (1-15 cm. long); sheaths membranaceous with a hyaline border and 

 ligule, usually lacerate : inflorescence a decompound, lax, one-sided, 

 more or less drooping umbel of numerous spikelets subtended by a 

 single erect, attenuate, terete bract, channeled only at the base (1-6 

 cm. long); rays 16 cm. long, slender, plano-convex, the margins 

 scabrous ; bractlets vaginate, light brown to chestnut, acute or acu- 

 minate scarious, pubescent toward the summit, hmbriate-ciliate, the 

 midrib excurrent into a scabrous tip ; secondary rays 0.5-4 cm. long, 

 slender : spikelets usually solitary or in capitate clusters of 2-3 

 (rarely 4 or 5) ferruginous to chestnut, ovoid to oblong-ovoid, acute 

 or becoming obtuse as terminal achenes mature, 3-4 by 5-10 (usually 

 7) mm.: scales equalling or slightly longer than the achenes and 

 rounded over them, broadly ovate or nearly orbicular, obtuse or 

 emarginate, spotted with chestnut or purplish brown, pubescent along 

 the midrib and at the summit with thick stubby hairs, ciliate; the 

 strong green or pale midrib exserted into a short scabrous tip : bristles 

 4-6 (usually 6) shorter, equalling or longer than the achene (usually 

 slightly longer), reddish brown, retrorsely barbed : style 2-cleft to 



