142 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Subgenus DICHANTHELITJM subgen. nov. 



Perennial, from a crown, rarely from short, matted rootstocks, surrounded by a more 

 or less well-marked rosette of usually short winter leaves, in spring producing simple 

 culms with mostly narrowly lanceolate blades and terminal panicles with numerous 

 spikelets, these rarely perfecting seed; the early culms branching at some or all of 

 the nodes (in a few species from the base only) after the maturity of the primary pani- 

 cles or sometimes before; the branches often repeatedly branching, the short branchlets 

 more or less fascicled and bearing usually much reduced leaves; the terminal one or 

 two joints of the primary culms often finally falling, the whole producing an autumnal 

 form usually strikingly different from the vernal form; the secondary panicles re- 

 duced, the latest more or less included in the sheaths, cleistogamous and perfecting 

 their grains. 



The type species is P. dichotomum L. 



In this group there is an intermediate stage of branching, in which the plants do 

 not show the characteristic vernal nor autumnal habit. Vernal culms are sometimes 

 produced on plants during the branched condition, because of renewal of activity, 

 due to increased moisture, excess of nutriment, injury, or other causes. 



SYNOPSIS OP GROUPS. 



Blades elongated, not over 5 mm. wide, 20 times as long as 

 wide; autumnal form branching from the base only (from 



the lower nodes in P. werneri) Depauperata (p. 151). 



Blades not elongated, (or if so, more than 5 mm. wide and 



autumnal form not branching from base). 

 . Plants branching from the base, finally forming rosettes or 

 cushions, foliage soft and lax ; blades prominently ciliate 



except in P. laxiflorum Laxiflora (p. 158). 



Plants branching from the culm nodes or rarely remaining 



simple. 



Blades long, stiff; autumnal form bushy-branched above. 



Spikelets turgid, attenuate at base; mostly pustulose- 



pubescent; blades conspicuously striate, tapering 



from base to apex Angustifolia (p. 165). 



Spikelets scarcely turgid, not attenuate at base; blades 



tapering to both ends Bicknelliana (p. 176). 



Blades not long and stiff (somewhat so in P. oligo- 

 santhes, P. malacon, P. commonsianum, and P. 

 equilaterale) ; not bushy-branched. 

 Plants not forming a distinct winter rosette; spikelets 



attenuate at base, papillose Pedicellata (p. 292). 



Plants forming a distinct winter rosette; spikelets not 

 attenuate at base. 

 Spikelets turgid, blunt, strongly nerved (not strongly 

 turgid in P. oligosanthes); blades rarely as much 

 as 1.5 cm. wide (sometimes 2 cm. in P. rav- 

 enellii and P. xanthophysum) . 

 Sheaths, or some of them, papillose-hispid (some- 

 times all glabrous in P. helleri); spikelets 3 to 4 



mm. long (2.7 to 3 mm. in P. wilcoxianum) Oligosanthia (p. 278). 



Sheaths glabrous or minutely puberulent; spikelets 

 1.5 to 2.5 mm. long, unsymmetrically pyri- 

 form; culms wiry Lancearia (p. 271). 



