Deutzia setchuenensis Franch. var. macrocarpa Q.L.Gan, Z.Y.Li & S.Z.Xu, 2023

Xu, Song-Zhi, Gan, Qi-Liang & Li, Zhen-Yu, 2023, Taxonomic notes on the genus Deutzia (Hydrangeaceae) from Central China, PhytoKeys 220, pp. 51-57 : 51

Deutzia setchuenensis Franch. var. macrocarpa Q.L.Gan, Z.Y.Li & S.Z.Xu var. nov.

Figs 1 , 2

Diagnosis.

The new variety, Deutzia setchuenensis Franch. var. Deutzia setchuenensis macrocarpa Q.L.Gan, Z.Y.Li & S.Z.Xu can be easily distinguished from other varieties (var. Deutzia setchuenensis setchuenensis , var. Deutzia setchuenensis corymbiflora (Lemoine) Rehder, var. Deutzia setchuenensis setchuenensis and var. Deutzia setchuenensis longidentata Rehder) by its orange anthers (vs. yellow anthers), broadly oblong outer filaments with 2 small repand denticles at apex, the width of teeth is more than twice its length (vs. oblong, with 2 deltoid, oblong or lanceolate teeth at apex, the length of teeth is equal to or more than its width), obtuse apex of inner filaments (vs. 2-dentata at apex), and larger fruits 5-7 mm in diam. (vs. 4-5 mm in diam.).

Type.

China. Hubei Province: Hongyangou village, Quanxi town, Zhuxi county , alt. 850m, 25 June 2022, Q.L.Gan 3306 (fl., holotype, PE!; isotype, PE!) .

Paratypes.

China. Hubei province: Hengduanshan, Baguashan Natural Reserve, Zhuxi county, alt. 840m, 13 June 2022, Q.L.Gan 3305 (fl., PE!); the same locality, 2 August 2022, Q.L.Gan 3307 (fr., PE!).

Description.

Deciduous shrubs, 90-150 cm tall. Old stems pale gray-brown, often with flaky bark; branches erect to spreading; branchlet opposite, sparsely gray stellate pubescent; flowering branchlets 8-14 cm, 6-10-leaved. Leaves opposite, stipules absent; petiole 3-5 mm long, sparsely stellate-pubescent; leaf blades papery, ovate to ovate-lanceolate, 2-10 cm long, 0.6-3 cm wide, base rounded to broadly cuneate, margin serrulate, apex acuminate or caudate-acuminate, adaxial surface green, not gloss, sparsely stellate pubescent, trichomes 2-4-rayed, abaxial light green, trichomes 4-6-rayed; lateral veins 2-4 paired, mid-vein and lateral veins impressed abaxially, and slightly prominent adaxially, veinlets inconspicuous. Cymes 2-3.5 cm long, 2-3 cm across, 6-12-flowered, sparsely stellate-pubescent; peduncle slender; pedicels 3-6 mm long, usually with 1 to 2 bracts at base or around the middle; bracts linear, 3-6 mm long, 0.5-1 mm wide; flower buds spheroical. Hypanthium hemispheric, 2.5-3.5 mm long and wide, densely 10-13-rayed stellate-tomentulose; calyx lobes 5, broadly deltoid, 1-1.5 × ca. 2 mm, apex acute, erect in bud, spreading in anthesis, inflexed and persistent in fruit. Corolla pure white; petals 5, white stellate-pubescent outside. Stamens 10 in 2-series, erect, filaments pure white, dorsiventraly flattened, anthers orange; outer stamens 4-5 mm long, filaments broadly oblong, with 2-repand denticles at apex, the width of teeth is more than twice its length, anthers broadly ovate; inner stamens shorter than outer ones, filaments obtuse at apex, anthers borne near middle of filaments abaxially, the width of anther exceeds the length. Disc annular, flattened, white. Ovary inferior, 2-3-loculed; styles 2-3, 3-3.5 mm long, usually coherent, glabrous. Capsule subglobose, 5-7 mm in diam., densely stellate-tomentulose, 2-3-valved. Seeds numerous, dark brown, ellipsoid or ovoid, 0.6-0.8 mm long, reticulate.

Phenology.

Flowering from May to June; fruiting from September to October.

Distribution and habitat.

Deutzia setchuenensis var. macrocarpa distributes in Quanxi town (Hongyangou village), Baguashan Provincial Nature Protection Area, and Taoyuan town (Hetaoyuan village) of Zhuxi county, Hubei province. It occurs at the edge of sparse thickets or forests on hillsides, or by streams. The main companion species include trees: Phoebe zhennan S. Lee, Sycopsis sinensis Oliv. and Symplocos lucida (Thunb.) Sieb. & Zucc.; shrubs: Rubus swinhoei Hance and Camellia cuspidata (Kochs) Wright ex Gard.; vines: Smilax glaucochina Warb. and Actinidia polygama (Sieb. et Zucc.) Maxim.; and a fern such as Dryopteris fuscipes C. Chr.

Etymology.

The Latin name of the variety, ' Dryopteris macrocarpa ', refers to the large fruit.

Vernacular name.

Da Guo Sou Shu (Chinese).

Conservation assessment.

Deutzia setchuenensis var. macrocarpa is currently known only from three localities consisting of less than 20 individuals in Zhuxi county, Hubei province. The provisional conservation status is Critically Endangered (CR), based on criterion D (number of mature individuals fewer than 50) ( IUCN 2022).

Economic uses.

Deutzia setchuenensis has rich intraspecific and morphological genetic diversity (Table 1 ). In the late 19th century, Deutzia setchuenensis var. setchuenensis and var. Deutzia setchuenensis corymbiflora (Lemoine) Rehder were introduced into western Europe, and it was found that the ornamental value and winter hardness of the former were inferior to the latter. The new variety has larger flowers and fruits, and utilization of its germplasm is potential.

Figures

Figure 1. Deutzia setchuenensis var. macrocarpa, var. nov. A plant B, C branches D petioles E leaves F flowering branches G fruiting branches.

Figure 2. Deutzia setchuenensis var. macrocarpa, var. nov. A flowering branch B flower bud C young fruit D flower E outer stamens F inner stamens G capsules H stellate-pubescent on adaxial surface of leaf blade I stellate-pubescent on abaxial surface of leaf blade J stellate-tomentulose on surface of capsules.