10. Micranthemum Michx. 

 Two species in the Western Hemisphere. 

 1. Micranthemum umbrosum (Walt.) Blake. Shade mud-flower. Fig. 699. 



Stems repent, freely branched, to 3 dm. long or more; leaves sessile, opposite, 

 succulent, rotund, 4-9 mm. wide; flowers small, white or purplish, solitary in 

 the axils of some of the middle leaves; pedicels to 1 mm. long; calyx 1.5-2 mm. 

 long, equally 4-cleft into oblanceolate lobes; corolla obliquely salverform, barely 

 equaling the calyx, the 4-lobed limb longer than the tube with upper lip developed; 

 appendage of the 2 stamens a mere tooth, the filaments with an appendage; 

 stigmas short; capsule about 1 mm. in diameter, globose, thin, with an evanescent 

 partition, several- to many-seeded. Globifera umbrosa (Walt.) J. F. Gmel. 



On mud or wet sand in low woods and along streams, in water of sluggish 

 streams, wet mud in swamps, often forming mats on edge of lakes, in e. Tex., 

 Apr.-Sept.; from Fla. to Tex., n. to Va.; also trop. Am. 



11. Penstemon Mitch. Beard-tongue 



Herbs or shrubs; leaves opposite, decussate, the lower often petiolate, the 

 upper sessile; pubescence (if present) glandular in the inflorescence, simple below; 

 inflorescence usually a narrow terminal panicle; sepals 5; corolla tubular, the 

 upper lip 2-lobed. the lower lip 3-cleft, the lower inner surface (floor) of the 

 throat and tube often with colored lines; stamens 4; staminode 1, filamentlike, 

 often bearded apically; anthers 2-chambered, these confluent if dehiscent across 

 the connective; capsules septicidal or else 4-valved; seeds many, usually multi- 

 angular, with a rough coat. Flowering from spring to fall. 



About 300 species; indigenous to America from Alaska to Guatemala, 



1. Distribution in eastern Oklahoma and/or eastern Texas (2) 



1. Distribution in New Mexico and Arizona (4) 



2(1). Floor of corolla strongly pleated; staminode densely bearded with golden 

 hairs for most of its length, exserted 1. P. laxiflorus. 



2. Floor of corolla rounded; staminode more lightly bearded with yeliow hairs, 



included (3) 



3(2). Corolla pink, 15-17 mm. long; leaves regularly sharply but shallowly 

 toothed 2. P. tenuis. 



3. Corolla white, 16-30 mm. long: leaves subentire or unevenly toothed 



3. P. Digitalis. 



4(1). Leaves (at least a few of them) toothed; corolla glandular externally 



4. P. Whippleanus. 



4. Leaves always entire; corolla not glandular externally (5) 



5(4). Throat of the corolla more or less distinctly 2-ridged within ventrally, the 

 ridges densely hairy about the orifice; leaves oblanceolate to 

 elliptic 5. P. Rydbergii. 



5. Throat of the corolla rounded ventrally, lightly if at all hairy at the orifice; 



leaves mostly linear 6. P. virgatus. 



1. Penstemon laxiflorus Penn. 



Plants 3-7 dm. tall, the stem and leaves glabrous to puberulent; leaves well- 

 toothed, those of the midstem 3.2-10.5 cm. long, 4-17 mm. wide, narrowly 

 lanceolate; inflorescence lightly glandular-pubescent; sepals 2-5 mm. long; corolla 

 white to pink, 22-30 mm. long, narrow, little-expanded, the floor prominently 

 pleated, lined within; staminode densely bearded with golden hairs for most of 

 its length, exserted; anther sacs cymbiform; seeds 1-1.5 mm. long. 



1487 



