282 



CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Fig. 317. — P. helleri. From type specimen. 



about 1 mm. long; blades ascending or spreading, measuring about the same as those 

 of P. scribnerianum, but broadest about the middle, rather thin, glabrous on both sur- 

 faces or pubescent beneath, ciliate toward the base; panicles finally rather long- 

 exserted, 6 to 12 cm. long, about three-fourths as wide, more open and loosely flowered 

 than in P. scribnerianum; spikelets 2.9 to 3 mm. long, 1.6 to 1.7 mm. wide, obovate, 

 turgid, blunt, glabrous, or with few scattered hairs; first glume about one-third the 

 length of the spikelet, acute; second glume and sterile lemma subequal, slightly 

 exposing the fruit at maturity, strongly nerved; fruit 2.4 to 2.5 mm. long, 1.5 to 1.6 

 mm. wide, oval, obscurely apiculate. 



Autumnal form branching at all but the lowest nodes, forming loose sprawling tufts, 

 the branches somewhat divaricate, with sheaths more commonly pubescent than those 



of the primary culm, the blades widely 

 spreading, not much reduced, the long- 

 pediceled spikelets rather conspicuous 

 among the foliage. 



This species is closely related to P. 

 scribnerianum, and many specimens are 

 but doubtfully differentiated. As here 

 distinguished, the smaller spikelets, thin- 

 ner blades tapering to both ends, and the 

 lax habit, taken in combination, have 

 been used to separate P. helleri. As in P. 

 scribnerianum little weight can be given to 

 pubescence or lack of it, hispid and glabrous sheaths being found on the same plant, as 

 in Bush 803 and Hitchcock 1173, though P. helleri is more commonly nearly glabrous 

 than is P. scribnerianum. Reverchon 's no. 2857 is probably referable to this species, 

 but the pubescence of culms, sheaths, and lower surface of blades and the long hairs 

 mixed with the short ligule show affinity to P. oligosanthes. The spikelets are 3 mm. 

 long, too immature to show turgidity. 



A few specimens are intermediate in the size of the spikelets. In Harvey 17 and 

 Hitchcock 1173 the spikelets are 3.1 to 3.2 mm. long; and Hitchcock 1223, with spikelets 

 3.3 mm. long, is referred here since the specimen shows the sprawling habit of P. 

 helleri. 



DISTRIBUTION. 



Open woods and prairies, Missouri and Oklahoma to Louisiana and New Mexico. 

 Missouri: Sheffield, Bush 803, 3903; Levasy, Bush 1685; Courtney, Bush 1710, 



3893. 

 Arkansas: Fulton, Bush 2529; northern Arkansas, Harvey 17. 

 Louisiana: Cameron, Tracy 8419. 

 Texas: Dallas, Bush 705, Rever- 



chon 1074 in part, 2444; Dallas 



County, Reverchon 2342, 2344, 



2345; Denison, Bebb 1430; 



Weatherford, Tracy 7949; Cor- 



sicana, Reverchon 2855 in part; 



Grand Saline, Reverchon 4138; 



Terrell, Warburton 2; Waller, 



Hitchcock 1173, 1179, 1186, 



1212; Waller County, Thurow 



in 1898; Houston, Bebb 1278, 



Hall 830, Nealleym 1887; Gal- 

 veston, Plank 82; Virginia Point, Bray 33; Kerrville, Heller 1759, Smith in 



1897; Burnet, Plank S; Velasco, Smith in 1897; Victoria, Tracy 8870; Kings- 



ville, Tracy 8885; without locality, Buckley in 1881. 

 Oklahoma: On the False Washita, Palmer 382 in 1868. 

 New Mexico: Mogollon Mountains, Metcalfe 354. 



Fig. 318.— Distribution of P. helleri. 



