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..
Annual or perennial herbs (some exotic species shrubs or trees), with opposite and alternate, rarely verticillate leaves, and mostly small blue purple pink or white flowers, terminal or axillary, racemose, spicate, or solitary. Calyx mostly 4-parted, sometimes 5-parted, the segments oblong or ovate. Corolla rotate, its tube very short, deeply and more or less unequally 4-lobed (rarely 5-lobed), the lower lobe commonly the narrowest. Stamens 2, divergent, inserted on either side and at the base of the upper corolla-lobe; anthers obtuse, their sacs confluent at the summit; filaments slender. Ovary 2-celled; style slender; stigma capitate; ovules few or numerous in each cavity. Capsule more or less compressed, sometimes very flat, emarginate, obcordate, or 2-lobed, loculicidally dehiscent. Seeds smooth or rough, flat, plano-convex, or excavated on the inner side. [Named for St. Veronica.]
About 200 species, of wide geographic distribution. Besides the following, 3 others occur in northwest America. Type species: Veronica officinalis L.
* Flowers racemose in the axils of the leaves, bracteolate.
Glabrous, or minutely glandular above (No. 3 rarely hairy); brook or swamp plants. Leaves ovate, oval, oblong, or oblong-lanceolate; capsule compressed. Stem leaves sessile, partly clasping, serrulate or entire.
1. V. Anagallis-aquatica.
All the leaves petioled, serrate.
2. V. americana.
Leaves linear or linear-lanceolate; capsule very flat.
3. V. scutellata.
Pubescent, dry soil plants; leaves crenate or dentate.
Leaves oval or obovate, petioled; pedicels shorter than the calyx.
4. V. officinalis.
Leaves ovate, nearly or quite sessile; pedicels longer than the calyx 5. V. Chamaedrys.
** Flowers in terminal spikes or racemes, or solitary in the axils.
Flowers in terminal spikes or racemes.
Leaves all sessile: capsule elliptic, emarginate.
6. V. Wormskioldii Lower leaves petioled; capsule orbicular, obcordate.
7. V. serpyllifolia.
Flowers solitary in most of the axils; peduncles shorter than the leaves. Erect; glabrous or glandular; capsule emarginate.
8. V. peregrina.
Diffuse; pubescent; capsule obcordate.
9. V. arvensis.
Flowers solitary in the axils; peduncles as long as the leaves, or longer. Leaves ovate or oblong, crenate or dentate.
Corolla not longer than the calyx; capsule narrowly emarginate.
10. V. agrestis.
Corolla longer than the calyx; capsule broadly emarginate.
11. V.Tournefortii Leaves orbicular, or broader, 3-5-lobed or -crenate.
12. V. hederaefolia.
Veronica Anagallis-aquatica L. Sp. Pl. 12. 1753.
Perennial by stolons or leafy shoots developed in autumn; stem rather stout, glabrous, or glandular-puberulent above, erect or decumbent, often rooting at the lower nodes, usually branched, 1°-3° high. Leaves of sterile autumn shoots orbicular to obovate, obtuse, serrulate, narrowed into margined petioles, those of the flowering stems ovate, oblong, or lanceolate, sessile and more or less clasping or the lowest short-petioled, serrulate or entire, 1 1/2' - 4' long, 1/4' - 2' wide; racemes peduncled, borne in most of the axils, 2'-5' long; bractlets shorter than or exceeding the pedicels; flowers blue, or purplish striped, 2" broad; capsule compressed, not very flat, nearly orbicular, 2-lobed, emarginate, 1 1/2" high; seeds flat.
In brooks and swamps, Nova Scotia to British Columbia, south to North Carolina, Nebraska and New Mexico. Also in Europe and Asia. The plant of the Atlantic Coast appears as if introduced. Ascends to 4000 ft. in Virginia. May-Sept.