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, erect branching or rarely simple, pubescent hirsute or hispid herbs, with alternate entire leaves, and small or large, white yellow or blue flowers in leafy-bracted spikes or racemes. Calyx 5-parted or 5-cleft, the segments or lobes narrow. Corolla funnel-form or salverform, 5- lobed, naked, pubescent or crested in the throat, the lobes entire or erose-denticulate, the tube sometimes pubescent at the base within. Stamens 5, included, inserted on the throat of the corolla; filaments short. Ovary 4-divided; style slender, or filiform; stigma capitate, or 2- lobed. Nutlets 4, or fewer, erect, white, smooth and shining, or brown and wrinkled, attached by their bases to the nearly flat receptacle, the scar of attachment not concave. [Greek, stone-seed, from the hard nutlets.]
About 40 species, natives of the northern hemisphere, a few in South America and Africa. Besides the following, some 7 others occur in the southern and southwestern parts of the United States. Type species: Lithospermum officinale L.
Corolla white or yellowish, its tube shorter than or equalling the calyx; flowers distant. Nutlets brown, wrinkled and pitted: annual or biennial.
1. L. arvense.
Nutlets white, smooth and shining; perennials. Leaves lanceolate, acute; nutlets ovoid.
2. L. officinale.
Leaves ovate, acuminate: nutlets globose-ovoid.
3. L. latifolium.
Corolla dull yellow, its tube longer than the calyx; leaves lanceolate; flowers dense.
4. L. pilosum.
Corolla bright yellow, its tube much longer than the calyx; flowers dense; red-rooted perennials. Corolla-lobes entire; flowers all complete.
Hispid-pubescent; corolla-tube bearded at the base within.
5. L. carolinense.
Hirsute, somewhat canescent; corolla-tube not bearded at the base.
6. L. canescens.
Corolla-lobes erose-denticulate: later flowers cleistogamous.
7. L. linear if oliutn.
Lithospermum arvense L. Sp. Pl. 132. 1753.
Annual or biennial, appressed-pubescent; stem erect, usually branched, 6 -20' high. Leaves bright green, lanceolate, linear or linear-oblong, sessile or the lowest short-petioled, mostly appressed, obtuse or acutish at the apex, narrowed at the base, indistinctly.veined, 1/2'- 1 1/2' long, V-3" wide, the uppermost smaller; flowers sessile or very nearly so in the spikes, becoming distant, white, about 3" long; calyx-segments linear-lanceolate, longer than or equalling the corolla-tube; corolla funnelform, puberulent in the throat but not crested; nutlets brown, wrinkled and pitted, glabrous, about 1" high, convex on the back, keeled on the inner side, one-third to one-half the length of the calyx-segments.
In waste places and fields, Quebec to Ontario and Michigan, south to Georgia and Kansas. Naturalized from Europe. Native also of Asia. Pearl-plant. Salfern-stoneseed. May-Aug.