—24— 



I. Ridges with two rows of tubercles. 



A. Diameter of centrum 1-3 to 2-3 that of stem, carinal bast 

 longer than vallecular, teeth more or less divaricate, the tips not 

 deciduous, sheaths light (in old or wet stems), ridges bluntly 

 biangulate Jcsupi. 



B. Diameter of centrum 1-3 that of stem, vallecular bast 

 usually longer, extending to the cavity, teeth broad, black and 

 white, with deciduous filiform tip. 



1. Stout, 2 lines in diameter, 1 to 2 feet high. Sheaths light. — 

 Alaskanum. 



2. Stems slender, tufted, 1 line in diameter, sheaths ampli- 

 ated Variegatum. 



II. Ridges rounded. 



Stems annual, sheaths ampliated when dry, close when fresh 

 or wet, centrum J / 2 the diameter Nelsoni. 



1. Jesupi A. A. Eaton. Stems 6 to 18 inches tall, 1 to 2 lines 

 in diameter, pale green, naked or branched the second year, 

 deeply 10 to 15 grooved, the ridges square or biangulate. Stomata 

 in a single rowed series, the valleculas with many distinct banded 

 or scattered rosulse in young stems, later obscured by a de- 

 posit of silex. Sheaths long, tight in fresh or wet stems, the 

 younger one contracted at the nodes when dry, the basal black, 

 the middle with black ring, the uppermost with black tips, be- 

 coming ashy and deciduous in fragments in old stems. Leaves 

 sharply four angled. Teeth not articulated to the sheaths, per- 

 sistent, grooved in the middle, broad, hyaline with narrow black 

 center, excurrent into a rough persistent awn i J / 2 times as long, 

 usually cohering in groups, variously spreading, at times fading 

 and withering. Central cavity 1-3 to 3-5 the total diameter, the 

 vallecular holes large, transversely oval, the vallecular bast small, 

 not separating the green parenchyma, while the carinal follows 

 the dissepiments nearly to the carinal canal, the arrangement 

 being just the opposite of variegatum, and as in the Hiemalia. 

 The ribs bear regular or fragmentary cross-bands, and become 

 biangulate by the lateral epidermal cells bearing a heavier deposit 

 of silex. It differs from variegatum in its size, the blacker 

 sheaths, persistent awns of the teeth, the broader keels with 

 deeper grooves, more sharply and irregularly tubercled on the 

 angles, the deciduous sheaths and the bast and parenchyma. Its 

 appearance is almost exactly like hiemale pumilum from which it 



