9. Rhododendron subg. Therorhodion (Maximowicz) Drude in Engler & Prantl, Nat. Pflanzenfam. 4(1): 37. 1889 [“Therorodion”].
叶状苞亚属 ye zhuang bao ya shu
He Mingyou (何明友); David F. Chamberlain
Rhododendron sect. Therorhodion Maximowicz, Mém. Acad. Imp. Sci. Saint Pétersbourg, Sér. 7, 16(9): 15, 47. 1870; Rhodothamnus Lindley & Paxton, Paxt. Fl. Gard. 1: 113. 1850, not Reichenbach (1827); Therorhodion (Maximowicz) Small.
Dwarf shrubs, deciduous; young shoots not scaly, sparsely glandular-hairy. Leaf blade thin, spathulate, spathulate-oblanceolate or obovate; margin sometimes glandular-ciliate, not scaly. Inflorescence terminal, umbellate-racemose, 1–3-flowered. Pedicels with glandular hairs and leaflike bracteoles; calyx well-developed, 5-lobed; corolla rotate, tube shorter to slightly longer than lobes; outer surface glabrous or pubescent; stamens 10; ovary 5-locular, hairy; style equaling or shorter than the corolla, curved, hairy towards base.
Three species: China, Japan, Russia; North America (Alaska); one species in China.
Recent evidence from DNA sequencing suggests that this subgenus is basal to the remaining subgenera of Rhododendron and supports the maintenance of the genus Therorhodion proposed for the three species included within it. It should be noted that the presence of bracteoles on the pedicels is unique in the genus Rhododendron.
