MANUAL OF THE GRASSES OF THE UNITED STATES 605 



Blades spreading; spikelets not turgid. 



Spikelets 2.2 mm long or more, pointed. Sheaths bearing pale 



glandular spots 33. P. yadkinense. 



Spikelets not more than 2 mm long, not pointed. 



Autumnal phase erect, branched like a little tree; primary blades 

 rarely more than 5 mm wide; second glume shorter than fruit 



and sterile lemma 31. P. dichotomtjm. 



Autumnal phase topheavy-reclining; primary blades 6 to 10 mm 

 wide; second glume equaling fruit and sterile lemma. 



32. P. BARBULATUM. 



7. Spreta 



Panicle narrow, one-fourth to one-third as wide as long 38. P. spretum. 



Panicle open, two-thirds as wide as long, or more. 



Spikelets 1.5 mm long 39. P. lindheimeri. 



Spikelets 1.3 mm long or less. 



Culms and sheaths glabrous 41. P. longiligulatum. 



Culms and sheaths appressed-pubescent. 



Spikelets 1.2 to 1.3 mm long 40. P. leucothrix. 



Spikelets not more than 1 mm long 42. P. wrightianum. 



8. Lanuginosa 



la. Spikelets not more than 2 mm long. 

 2a. Plants grayish, velvety-pubescent. 



Spikelets 1.4 to 1.5 mm long; autumnal blades involute-pointed (see also 



P. albemarlense) 49. P. auburne. 



Spikelets 1.8 to 2 mm long; autumnal blades fiat. 



Plants dark or olive green when dry; spikelets 1.9 to 2 mm long. 



50. P. THUROWII. 

 Plants light or yellow green when dry. 



Autumnal phase prostrate, branching from base and lower nodes, 

 forming close mats; blades not ciliate. Around hot springs. 



55. P. thermale. 

 Autumnal phase ascending or spreading, branching from middle and 

 upper nodes, the reduced, fascicled blades strongly ciliate. 



48. P. lanuginosum. 

 2b. Plants pubescent, often villous, but not velvety. 



3a. Culms conspicuously pilose with long, horizontally spreading hairs. 

 Culms branching before expansion of primary panicles. 



51. P. PRAECOCIUS. 



3b. Culms variously pubescent, if pilose the hairs not long and horizontally 

 spreading. 

 4a. Vernal blades glabrous or nearly so on the upper surface, firm in tex- 

 ture. 

 Autumnal culms branching from the lower nodes, forming a spreading 



bunch 10 to 15 cm high; Pacific slope 53. P. occidentale. 



Autumnal culms branching from the middle nodes, forming widely 

 spreading mats; Atlantic slope (see also form of P. huachucae var. 



fasciculatum) 47. P. tennesseense. 



4b. Vernal blades pubescent on upper surface, sometimes pilose near base 

 and margins only. 

 5a. Spikelets 1.3 to 1.5 mm long; vernal blades long-pilose on upper 

 surface. 

 Autumnal phase widely decumbent-spreading, forming a mat; vernal 

 culms soon geniculate-spreading; plants olivaceous. 



44. P. albemarlense. 

 Autumnal phase erect or leaning, never forming a mat; plants yellow- 

 ish green. 

 Axis of panicle pilose, panicle branches tangled, the lower drooping. 



45. P. IMPLICATUM. 



Axis of panicle puberulent only, panicle branches not tangled, the 



lower ascending 43. P. meridionale. 



5b. Spikelets 1.6 to 2 mm long; vernal blades pilose or pubescent. 

 Upper surface of blades pilose; spikelets 1.8 to 2 mm long; autumnal 

 phase decumbent-spreading. 

 Spikelets pointed; culms weak and lax_,^_, 56, P. LANGUiDrjM. 



