Addisonia 19 



(Plate 130) 



PENSTEMON DIGITALIS 

 Foxglove Beard-tongue 



Native of the southwestern Mississippi Valley 

 Family ScrophuIvAriaceae Fig wort Family 



Penstemon Digitalis Nutt. Trans. Am. Phil. Soc. II. 5: 181. 1837. 



A glabrous herbaceous plant, from a short rootstock sending up 

 one or a few slender stems, each terminating in a panicle of many 

 white flowers. The erect stems are two to four feet tall. The 

 leaves are of two types: those of the winter rosette, in summer 

 persisting at the base of the stem, are prevailingly ovate and petioled ; 

 those of the stem itself are narrower and sessile, the upper clasping 

 by a rounded base; all are light-green, slightly paler beneath, with 

 denticulate to nearly entire margins. The panicle, about one third 

 the height of the plant, is rounded-pyramidal, composed of pairs of 

 branches borne in the axils of much reduced bract-like leaves; each 

 branch terminates in two flowers subtended by a pair of bracts, 

 from the axils of which two new branches arise to repeat the process 

 — a peculiar branching usually repeated for several stages further. 

 The flowers are borne on pedicels about one fourth of an inch in 

 length. The five sepals are usually slightly longer than this, 

 lanceolate and long-attenuate, and, like the pedicels, are slightly 

 pubescent with stalked dark brown glands. The corolla is about 

 one inch long; the basal third, the "tube," is narrow and horizon- 

 tally flattened; distally from this is the "throat," strongly inflated, 

 arched posteriorly and slightly two-ridged within anteriorly, with 

 an open mouth; the five corolla-lobes are ovate and rounded, the 

 two posterior, forming the upper lip, upcurved and somewhat 

 spreading, the three anterior deflexed-spreading ; the corolla is white 

 throughout, or usually" with violet lines within on the anterior side; 

 externally it is finely pubescent with gland-tipped hairs, and within 

 the mouth over the bases of the anterior lobes it is pubescent with 

 white hairs. The five stamens, alternate with the corolla-lobes, 

 are remarkably modified: the posterior, which is deflected to lie 

 against the anterior lip, is sterile, forming no anther, the white 

 flattened filament bearing on its posterior face a bristle-like beard 

 of yellow hairs; the others, which all develop anthers, have filaments 

 of two lengths, the antero-laterals longest, and are arched so that 

 the anthers approximate in pairs against the posterior side of the 

 throat; the four anthers are alike, each of two widely-divaricate 

 oblong, violet-gray, usually pubescent sacs, each sac opening by a 

 slit its entire length. The pistil is of two carpels, with a two-celled 

 ovary, a slender white style, and a small capitate stigma. The 

 pyramidal woody-walled capsule opens by splitting from the apex 

 for a portion of its length, the primary fissure dividing the partition- 

 wall between the cells, the secondary slighter fissure opening some- 



