7. Hypericum lobocarpum Gatt.

H. densiflorum Pursh var. lobocarpum (Gatt.) Svenson

Pl. 362 g, h; Map 1567

Plants shrubs, sometimes woody only toward the base, to 1.5 m tall. Stems erect or ascending. Bark reddish brown, smooth, usually peeling in thin strips. Twigs angled or slightly ridged below each leaf, reddish brown, the older stems usually rounded but often with longitudinal lines below the leaves. Leaves jointed at the base. Leaf blades 15–50 mm long, 3–12 mm wide, narrowly oblong to oblanceolate or less commonly linear, rounded to bluntly pointed at the tip (often with a minute, sharp point), tapered or narrowed to a petiole-like base, the margins rolled under at maturity, herbaceous to somewhat leathery in texture, with 1 main vein sometimes faintly visible, the surfaces lacking noticeable black dots, lines, or streaks but usually with minute, faint, pale dots visible, the upper surface green, the undersurface pale green and often somewhat glaucous. Inflorescences clusters of mostly 3–17 flowers, at the branch tips and from the axils of the uppermost leaves, appearing paniculate. Flowers actinomorphic. Sepals 5, all similar in size and shape, 3.5–4.5 mm long, not becoming enlarged at fruiting, narrowly elliptic to narrowly oblong-oblanceolate, the margins often somewhat curled, lacking noticeable yellowish brown or black dots, lines, or streaks. Petals 5, 6–8 mm long, oblanceolate to obovate, yellow to orangish yellow, usually shed before fruiting. Stamens 100–150, the filaments not fused into groups. Ovary incompletely mostly 4- or 5-locular, the placentation more or less axile. Styles mostly 4 or 5 (some 3-styled flowers present in Missouri material), free above the base, but erect and more or less appressed at flowering, persistent and usually separating somewhat as the fruit matures, the stigmas minute. Fruits 5–7(–8) mm long, narrowly ovoid or somewhat conical, widest below the midpoint, tapered to the beak(s), noticeably lobed longitudinally and appearing mostly 4- or 5-lobed in cross-section. Seeds numerous, 1.2–1.5 mm long, the surface with fine longitudinal lines, these sometimes forming a faint network, dark brown to nearly black. 2n=18. June–September.

Uncommon, known only from historical collections from Howell and Ripley Counties (Illinois, Kentucky, and Tennessee west to Oklahoma and Texas). Openings of sandy upland forests and fens.

The situation with this taxon in Missouri is complicated. Steyermark (1963) reported both H. lobocarpum (as H. densiflorum var. lobocarpum) and the closely related H. densiflorum for Missouri. However, H. densiflorum, which differs in its mostly 3-locular ovaries, unlobed capsules, and details of sepal venation, occurs only to the southeast and east of Missouri. Nowhere does its range overlap with that of H. lobocarpum (Adams, 1962; Robson, 1996). Steyermark noted, however, that Preston Adams, who was then preparing a monograph of the group (Adams, 1962), had suggested that the single collection attributable to H. densiflorum was in fact H. lobocarpum. Hypericum densiflorum subsequently was excluded from the flora by Yatskievych and Turner (1990), as well as in the present treatment. Adams, however, further noted in his annotations of the Missouri specimens that although they were closest to H. lobocarpum, they possibly represented hybrids between that species and H. prolificum. Adams (1972) discussed hybridization between H. lobocarpum and H. prolificum, for which the binomial H. Hdawsonianum Rehder was published describing hybrids that arose spontaneously from adjacent plantings of the two parental taxa at the Arnold Arboretum. The Missouri specimens are intermediate insofar as they possess some 3-styled flowers in each inflorescence (a character of H. prolificum and H. densiflorum), but they otherwise resemble H. lobocarpum. The status of H. lobocarpum in Missouri thus requires further study to resolve whether the species is truly a member of the Missouri flora or whether the few historical collections represent isolated instances of hybrids spreading into southernmost Missouri from adjacent mixed parental populations in Arkansas. A historical specimen from Dunklin County reported by Steyermark (1963) could not be located during the present study and was not mapped by Adams (1962) or Robson (1996).