Hypericum frondosum (Nomenclature)
Shrub (0.6-)l-3 m tall, erect, much branched above base, with branches lateral, strict to spreading, forming rounded bush or small 'tree'. Stems green, 4-lined and ancipitious when young, soon 4- lined and rounded, becoming reddish brown and 2-lined to terete in 2nd or 3rd year; cortex exfoliating in strips or (often large) plates; bark pale grey, smooth, thin. Leaves sessile, ascending to spreading; lamina 25-65 x 8-22 mm, oblong to lanceolate-oblong or some- times narrowly elliptic to oblanceolate, plane or with margin subrecurved, paler or somewhat glaucous beneath or wholly glaucous, chartaceous, deciduous at basal articulation, apex apiculate- obtuse to rounded, base broadly cuneate and attenuate to narrowly cuneate; venation sometimes rather obscure: c. 10-16 pairs main laterals with subsidiaries and densely reticulate tertiaries, midrib prominent; laminar glands dense. Inflorescence l-3(-7)-flowered, sometimes with paired single flowers or triads or 1-3-flowered branches at node below and very rarely single flowers at third node ('H. splendens'); pedicels 1.5 (terminal)-l0 mm long; bracts foliar or reduced, oblong-elliptic. Flowers 25-45 mm in diam.; buds globose. Sepals 5(4), 6-14(-20) x 4-10 mm, enlarging in fruit, imbricate, very unequal, ovate or oblong to elliptic or elliptic- spathulate or sometimes foliaceous, rounded or apiculate-obtuse, plane or margin recurved, basal veins (3)5-7(9), branching and densely reticulate distally. Petals 5(4), golden yellow to orange- yellow, base soon brownish, becoming incurved-deflexed, 12-25 x 6-14 mm, 1.25-2 x sepals, obovate to oblanceolate, with apiculus lateral (petals sometimes bifid), rounded. Stamens c. 250-650, longest 9-12 mm, 0.45-0.75 x petals. Ovary 3-merous, 6-8 x 3-4(-5) mm, narrowly pyramidal-ovoid to broadly ellipsoid, acute to apiculate-obtuse, placentation incompletely axile; styles 3, 4-6 mm long, 0.65-0.75 x ovary, remaining erect. Capsule 12-15 x 6-8 mm, narrowly ovoid-conic to broadly ovoid-rostrate, rounded-trigonous, exceeding or shorter than sepals and often initially surrounded by them, thickly coriaceous. Seeds blackish brown, c. 1.5 mm long, carinate; testa shallowly linear-reticulate.
2n = 18 (Hoar & Haertl, 1932; Adams in Robson & Adams, 1968), 36 (see note below).
Dry cedar glades and barrens on limestone and calcareous shales, also (Demaree 405749) 'swampy creek bottoms'; 180-506 m.
U.S.A. (southwestern end of the Appalachian Range), in northern and central Georgia, northern Alabama, eastern Mississippi, northern Louisiana, eastern Tennessee and southern Kentucky; also recorded from eastern Texas. Adventive in Connecticut, New York and Massachusetts (fide Adams, 1962).
H. frondosum has the most primitive characters of any species in sect. Myriandra, its nearest (ancestral) species being H. synstylum N. Robson from Ethiopia and Somalia (sect. 1 . Campylosporus). Only one character, trimery of the gynoecium, might be regarded as special- ised in comparison with 3. H. kalmianum L. and 4. H. lobocarpum Gatt. Since these species, however, are much more specialised in their other characters, there are grounds for assuming that pentamery of the gynoecium is advanced, not primitive, in this section; and its constant trimery in H.frondosum would support this assumption. H.frondosum is the nodal species in sect. Myriandra, being related to species in three subsections. Through 2. H. prolificum it is related to the rest of subsect. Centrosperma, through 23. H. myrtifolium to subsect. Brathydium, and through 25. H. crux-andreae to subsect. Ascyrum. From H. prolificum it can be distinguished (at least in natural habitats) by the larger leaves, flowers and fruits and by the virtual restriction of the inflorescence to the terminal node. When flowers are present at lower (1-2) nodes, they are solitary or rarely 3 in each leaf axil. The larger floral parts also help to distinguish H. frondosum from the other two related species. In addition, H. myrtifolium has cordate-amplexicaul leaves, whilst H. crux-andreae has a tetramerous perianth and spreading styles. At least in cultivation, H. frondosum itself produces a few flowers with a tetramerous perianth, thus indicating where 'Ascyrum ' has been derived from Hypericum. The flowers of H. frondosum rarely exceed 45 mm in diameter, and the diploid chromosome number is normally
18. One specimen in the Arnold Arboretum herbarium (A), however, has a flower 60 mm in diameter and is labelled as a tetraploid (2n = 36). It was collected from the Arboretum Trial Ground (J. W. Peterson J-196). Perhaps the extraordinarily large-flowered cv. Sunburst is also tetraploid. Colchicine-induced tetraploids of this species have been produced (Myers, 1963).