32 POACEAE. 



40. UNIOLA L. Usually tall perennial grasses, with flat or convolute 

 leaf-blades and contracted or open panicles, the branches sometimes nodding. 

 Spikelets many, erect, or sometimes nodding, laterally compressed, 2-edged, 3- 

 many-flowered, the flowers perfect or the upper ones staminate. Scales 6-many, 

 compressed-keeled, sometimes winged, the lower 3-6 empty, gradually enlarging, 

 the flowering scales many-nerved, similar to the upper ones of the lower empty 

 scales but larger, the remaining scales, if any, empty; palet somewhat rigid, 

 2-keeled, the keels narrowly winged. Stamens 1-3. Styles distinct. Stigmas 

 plumose. 



1, U. latifolia Michx. Stems 6-15 dm. tall: leaf -blades 1-2.5 dm. long, 6-25 

 mm. wide: panicle lax, 1.5-2.5 dm. long: spikelets many-flowered, oval to ovate, 

 much flattened, 2.5-4 cm. long, on long capillary pendulous pedicels, the flower- 

 ing scales 9-12 mm. long, ciliate-hispid on the winged keel. — Susquehanna 

 valley. Rather rare, on the river shore and islands. — Schists. — Sum. — Spike- 

 grass. 



41. DACTYLIS L. Perennial usually tall grasses, with flat leaf -blades 

 and open or contracted panicles. Spikelets in head-like clusters which are 

 unilaterally arranged and crowded at the ends of the branches, 3-5-flowered, 

 the flowers perfect or the upper ones staminate. Scales 5-7, keeled, the 2 lower 

 empty, unequal, mucronate, the second the larger, the flowering scales larger, 

 more rigid, the keel ciliate and excurrent as a mucro or short awn; palet nearly 

 as long as the scale, 2-keeled. Stamens 3. Styles distinct. Stigmas plumose. 



1. D. glomerata L. Stems 6-12 dm. tall: leaf -blades 7-23 cm. long, 2-6 mm. 

 wide: panicle 7-20 cm. long: spikelets in dense capitate clusters, 3-5-flowered, 

 the flowering scales 4-6 mm. long, rough, pointed or short-awned, ciliate on 

 the keel. — Common, on roadsides and in fields and orchards. Nat. of Eu. — 

 Sum. — Orchard-grass. 



42. POA L. Annual or perennial grasses, rarely dioecious, with flat leaf- 

 blades and open sometimes contracted panicles, the branches often drooping. 

 Spikelets 2-6-flowered, the flowers perfect, or rarely unisexual, the glabrous or 

 rarely somewhat pilose rachilla articulated between the flowers. Scales 4-8, 

 membranous, keeled, acute or obtuse, awnless, the 2 lower empty, persistent, the 

 flowering scales usually longer, frequently pubescent on the callus and the mid- 

 nerve and marginal nerves, the hairs often long and curled; palet shorter than 

 the scale, 2-nerved or 2-keeled. Stamens 3. Styles short, distinct. Stigmas 

 plumose. — Meadow-grass. Spear-grass. Blue-grass. 



Annuals or biennials : stems densely tufted, low, usually less tlian 3 dm. long. 



1. P. annua. 

 Perennials : stems usually exceeding 3 dm. tall. 

 Plants green with no long rootstocks. 



Flowering scales with long crimped hairs at the base. 



Flowering scales with only the midneive pubescent. 2. P. trivialis. 

 Flowering scales with the midnerve and lateral 

 nerves pubescent. 

 Midnerve of the flowering scale pubescent only 

 below the middle. 

 Flowering scales 2-3 mm. long : basal leaves 



usually relatively short. 3. P. pratensis. 



Flowering scales 4-5 mm. long : basal 

 leaves very long, often equalling the 



stem or nearly so. 4. P. hrachyphylla. 



Midnerve of the flowering scale pubescent the 



whole length, or nearly so. 5. P. sylvestris. 



