This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Erect branching annual or perennial herbs, some South American species shrubby, mainly with opposite and sessile leaves. Flowers showy, usually large, purple, violet, yellow, red, or rarely white, racemose, or paniculate, or solitary and axillary. Calyx campanulate, 5-toothed, or 5-lobed. Corolla somewhat irregular, campanulate, or funnelform, the tube broad, short, or elongated, the limb 5-lobed, slightly 2-lipped, the lower lobes exterior in the bud. Stamens 4, didynamous, included; filaments more or less pubescent; anthers 2-celled, their sacs obtuse or mucronate at the base, style filiform. Capsule globose or ovoid, loculicidally dehiscent, many-seeded. Seeds numerous, mostly angled. [Greek, remarkable flax.]
About 45 species, natives of America. Besides the following, some 10 others occur in the southern United States. Most of the species blacken in drying. Type species: Agalinis palustris Raf. (Gerardia purpurea L.) The generic name Gerardia (Plunder) L., used for these plants in our first edition, is typified by Gerardia tuberosa L. (Stenandrim tuberosum (L.) Britton, of the Acanthaceae).
Pedicels in flower shorter than the calyx, or but 1-2 times as long. Corolla 10"-13" long.
Calyx-teeth minute; root perennial.
1. A. linifolia.
Calyx-teeth triangular, lanceolate or oblong, acute; annuals. Leaves very scabrous, filiform; capsule oblong.
2. A. aspera.
Leaves slightly scabrous, linear; capsule globose. Calyx-teeth as long as the tube or longer.
3. A. heterophylla.
Calyx-teeth shorter than the tube.
4. A. purpurea.
Stem scabrous; branches virgate; leaves much clustered in axils.
A. fasciculate Corolla 5"-8" long.
Calyx-teeth triangular-subulate, acute.
6. A. paupercula.
Calyx-teeth broad, short, obtuse.
7. A. maritima.
Pedicels in flower 2-6 times as long as the calyx.
Leaves flat, linear, spreading or ascending; capsule globose. Leaves 1/4"-1" wide, 1/2' - 1 1/2' long; pedicels spreading.
8. A. tenuifolia.
Leaves 1"-2" wide, 1 1/2' -3' long; pedicels ascending.
9. A. Besseyana.
Leaves subulate, or filiform, the margins often revolute. Corolla-lobes obcordate or deeply emarginate.
10. A. parvifolia.
Corolla-lobes rounded or slightly emarginate. Corolla 5"-7" long; pedicels erect-ascending.
11. A. Skinneriana.
Corolla 8"-10" long; pedicels spreading-ascendmg. Calyx-teeth broadly triangular.
12. A. setacea.
13. A. Gattingeri.
Gerardia linifolia Nutt. Gen. 2: 47. 1818
Perennial, glabrous and smooth; stem branched, 2°-3° high. Leaves narrowly linear, rather thick, 1' - 2' long, 1"- 1 1/2" wide, erect the upper much smaller and subulate; pedicels erect, in flower equalling or a little longer than the calyx, longer in fruit; calyx campanulate, truncate, its teeth minute; corolla purple, about 1' long, narrower than that of the two following species, villous within, the lobes ciliate; filaments and anthers densely villous; anther-sacs mucronate at the base; capsule globose, 2" - 3" in diameter, but little longer than the calyx.
In moist pine barrens, Delaware to Florida. Aug.-Sept.