9. Lithospermum L. (puccoon)

Plants perennial herbs, with rhizomes or taproots, the rootstock sometimes somewhat woody, often with a purple pigment that leaches out when the tissue is bruised or in pressed specimens. Stems erect or ascending, sometimes from a spreading base, solitary or few to several, unbranched or more commonly few- to several-branched, moderately to densely pubescent with relatively soft and/or stiff, sometimes pustular-based hairs. Leaves alternate and sometimes also basal, but the basal leaves usually withered or absent at flowering, in some species the lower stem leaves reduced and scalelike. Stem leaves sessile or very short-petiolate, the blade variously shaped, the surfaces moderately to densely hairy, in L. latifolium the lateral veins prominent. Inflorescences not paired, of solitary flowers in the axils of the upper leaves or appearing as dense terminal clusters, these sometimes subsequently elongating into ascending, scorpioid, spikelike racemes, the flowers with stalks 1–4 mm long, each subtended by a leaflike bract. Cleistogamous flowers sometimes present, produced after the open flowers, solitary or in small clusters at the tips of short axillary branches. Calyces more or less actinomorphic but 1 or 2 of the lobes usually somewhat longer and/or wider than the others, 5-lobed nearly to the base, the lobes becoming somewhat elongated at fruiting, linear to narrowly triangular or narrowly lanceolate, hairy, persistent and ascending at fruiting. Corollas narrowly funnelform to trumpet-shaped, actinomorphic, yellow to orange or white to greenish white, the tube conspicuous, the throat usually with 5 small, scalelike appendages but these sometimes inconspicuous, hairy on the outer surface, sometimes only in lines. Stamens variously attached in the corolla tube (correlated with short-styled vs. long-styled flowers), the filaments short, the anthers oblong, not or only slightly exserted from the corolla. Ovary deeply 4-lobed, the styles often of different lengths in different plants of the same species (heterostylous), not or rarely slightly exserted from the corolla, often not persistent at fruiting, the stigma capitate, 2-lobed. Fruits dividing into usually 4 nutlets (in some species routinely only 1 or 2 nutlets), these erect to slightly oblique, ovoid with a blunt ventral keel, attached to the relatively flat gynobase at the base, the attachment scar surrounded by a low, collarlike ring, bluntly pointed at the tip, the surface smooth or pitted (mostly near the keel), white to ivory-colored or pale yellowish brown, shiny. About 45 species, nearly worldwide except Australia, most diverse in North America.

Eight of the species currently included in Lithospermum exhibit the phenomenon known as heterostyly, in which different plants in a given population produce flowers that are either short-styled or long-styled (Johnston, 1952; Al-Shehbaz, 1991). Correlated with this is usually a difference in the position of the stamens, with short-styled flowers having stamens attached higher in the tube and anthers positioned above the stigma, whereas in long-styled flowers the stamens are attached below the midpoint of the tube and the anthers are positioned below the stigma. Additionally, some species regularly produce cleistogamous flowers from short axillary branches in the leaf axils later in the growing season. Such flowers have small corollas that remain closed over the stamens and ovary and are shed as the fruits mature.

Species of Lithospermum have a long history of medicinal and ceremonial use by various cultures in North America and Asia (Al-Shehbaz, 1991; Moerman, 1998). Various species with roots that produce a purple or red dye have been used to color fabrics, for body decoration, and as food colorants. The common name puccoon apparently was derived from a Native American word for a dye plant. Nowadays, species of Lithospermum mainly are cultivated as garden ornamentals.