762 MISC. PUBLICATION 4 2 3, U. S. DEPT. OF AGRICULTURE 

 1. VERBENA. 28 Vervain 



Plants mostly biennial or perennial; flowers sessile, in elongate 

 spikes, these often forming panicles, or in short headlike clusters; 

 corolla salverform, the tube often curved; stamens included; style 

 slender; stigma often 2-lobed; nutlets elongate, normally 4. 



The species, especially in section Glandularia, are difficult to dis- 

 tinguish. It is believed that natural hybrids are of frequent occur- 

 rence in this genus. 



Key to the species 



1. Flowers showy, greatly surpassing the bracts, in short, broad, dense spikes, 



these becoming elongate and more open in fruit; corolla usually bright pink 



or mauve (rarely violet), 9 mm. long or longer: Section Glandularia (2). 



2. Leaf blades coarsely crenate-dentate and often shallowly cleft, the teeth or 



lobes not or but slightly longer than wide, obtuse or rounded at apex, the 



lobes (if any) approximate, with narrow sinuses; bracts lanceolate, shorter 



than the calyx; stems copiously villous or subhirsute, also finely puber- 



ulent and often glandular 1. V. gooddingii. 



2. Leaf blades 3-parted, the primary divisions pinnatifid, the ultimate divisions 

 narrowly lanceolate to oblong, considerably longer than wide, com- 

 monly acute or acutish; stems and leaves hirsute-hispid (3). 

 3. Stems widely spreading or prostrate, commonly less than 25 cm. long; 

 plant often grayish, copiously to densely pubescent; leaves very 

 crowded and overlapping, more or less appressed to the stem, not 

 more than 3 cm. long, the lobes approximate (much less than 1 cm. 

 apart), their margins often strongly revolute; spikes sessile or nearly 



so; bracts commonly shorter than the calyx 2. V. ciliata. 



3. Stems erect to decumbent-ascending, commonly more than 25 cm. long; 



plant usually green, not densely pubescent; leaves not very crowded, 



not appressed to the stem, mostly more than 3 cm. long, the lobes 



often 1 cm. or more apart; spikes usually distinctly pedunculate (4). 



4. Glandular puberulence none; bracts with long, setaceous tips, usually 



equaling or nearly equaling the calyx 3. V. bipinnatifida. 



4. Glandular puberulence present at least on the calyx, but sometimes very 

 obscure; bracts with shorter, often barely setaceous tips, consider- 

 ably shorter than the calyx 4. V. wrightii. 



1. Flowers not showy or greatly surpassing the bracts (except in V. neomexicana) , 



in' narrow, elongate spikes or if the spikes relatively short and broad at 



first then the bracts greatly surpassing the flowers; corolla whitish, blue, 



or violet, not more than 6 mm. long: Section Verbenacea (5). 



5. Bracts conspicuous, much surpassing the flowers, commonly at least 5 mm. 



long; stems strongly decumbent or prostrate, diffusely branched from at 



or near the base; leaf blades not or not much longer than wide, more or 



less incised (6). 



6. Leaf veins conspicuously whitish beneath toward the margin; blades 



incised -serrate or, at most, shallowly cleft; corolla dark blue; plant 



short-hirsute and glandular-puberulent 5. V. plicata. 



6. Leaf veins not conspicuously whitish; corolla pale blue; plants hispid- 

 hirsute (7). 

 7. Blades very deeply incised, the terminal division several-cleft nearly to 

 the midvein; spikes much less than 1 cm. wide; inflorescence 



copiously glandular; plant not drying blackish 6. V. gracilis. 



7. Blades not very deeply incised, the terminal division coarsely toothed 

 or, if cleft, then not nearly to the midvein; spikes commonly at 

 least 1 cm. wide; inflorescence not or obscurely glandular; plant 



often drying blackish 7. V. bracteata. 



5. Bracts inconspicuous, not or barely surpassing the flowers; stems erect or 



strongly ascending, not diffusely branched from the base (8). 



8. Corolla white or whitish, barely surpassing the calyx, about 2 mm. long, 



the limb not more than 3 mm. in diameter; fruits divaricate; spikes 



filiform, very long, loose, more or less flexuous; leaf blades coarsely 



crenate-dentate, never pinnatifid; bracts minute (9). 



28 Reference: Perry, Lily M. a revision of the north American species of verbena. Mo. Bot. 

 Gard. Ann. 20: 239-362. 1933. 



