GRASSES OF OHIO 311 



Subfamily, Panicatae. 

 Tribe, Paniceae. Panic-grass Tribe. 



Grasses having the 2-flowered spikclets rounded or dorsally com- 

 pressed, jointed below the empty glumes, and arranged in racemes or 

 panicles; lower flower staminate, vestigial or entirely absent; empty 

 glumes membranous ; flozvering glumes of the perfect flower usually 

 awnless, indurated, firmly enclosing the free grain. 



53. Panicum L. Panic-grass. 



Annual or perennial grasses of various habit with the spikelets 

 in panicles. Spikelets 2-flowered, with 1 perfect flower and with 

 a staminate or vestigial one below ; empty glumes very unequal, the 

 outer often minute ; sterile lemma membranous often enclosing a 

 hyaline palet ; fertile lemma and palet indurated in fruit, margins of 

 the lemma thick and inrolled ; grain free, enclosed in the hardened 

 flowering glumes. 



1. Basal leaves like those of the stem. 2 



1. Basal leaves unlike those of the stem. 10 



2. Basal leaf-sheaths compressed, often keeled. 3 



2. Basal leaf-sheaths round, little flattened, never keeled. 4 



3. Fruit stipitate; spikelets conspicuously secund. P. stipitatum. 



3. Fruit not stipitate; spikelets not conspicuously secund. P. agrostoides. 



4. Leaf-sheaths smooth. 5 



4. Leaf-sheaths pubescent ; annuals. 6 



5. Outer empty glume about Y> as long as the spikelet; tall perennials with 

 rhizomes. P. virgatum. 



5. Outer empty glume about Y as long as the spikelet; annuals. 



P. dichotomiflorum. 



6. Spikelets ovate, more than % in. long; spikelets close. P. miliaceum. 



6. Spikelets lanceolate or elliptic, less than % in- long ; spikelets distant. T 



7. Panicle narrow, the branches ascending; spikelets less than Y in. long. 



P. flexile. 



7. Panicle spreading when mature ; spikelet tV in. long or less. 8 



8. Panicle very large, usually l / 2 the length of the plant. P. capillare. 



8. Panicle of medium size, usually Yz the length of the plant. 9 



9. Stem delicate; leaf-blade less than Ya in. wide. P. philadelphicum. 

 9. Stem stout; leaf-blade usually Y~ 3 A in. wide. P. gat ting eri. 



10. Leaf-blades l / 2 way up the stem less than Y> in. wide, attenuate to cordate 

 at the base. 11 



10. Leaf-blades Y way up the stem Yz in. or more wide, usually cordate clasp- 

 ing at the base. 30 



11. Spikelets % in. long or more. 12 



11. Spikelets less than Y$ in. long, usually about & in. 22 



12. Leaves less than -?n in. wide and about 18 times as long as wide. 



P. de pauper atutn. 



12. Leaves more than % in. wide, and not elongated. 13 



13. Upper surface of the leaves glabrous. 14 



13. Upper surface of the leaves pubescent. P. leibergii. 



