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| Croton nagaoi Tagane, Soulad. & Souvann., in Tagane, Souvannakhoummane & Souladeth, 2022. ເປົ້າດົງ || DOI: 10.11646/phytotaxa.570.2.1 |
Abstract
Croton nagaoi (Euphorbiaceae) is described based on a specimen collected from the basin of the Bolaven Plateau, southern Laos. It is most similar to Croton thorelii Gagnep. of Laos, Cambodia, Thailand and Vietnam in size and shape of lamina, short petioles less than 1 cm long, and basal glands lateral on the abaxial midrib base, but different in having densely stellate hairy lower leaf surface (vs. very sparsely pubescent and glabrescent in C. thorelii), smaller sepals and petals of staminate flowers (sepals and petals ca. 2.2 mm long vs. 3 mm long and 2.5 mm long, respectively), and the presence of petals in pistillate flowers (vs. absent). Morphological descriptions, photographs, vernacular name, and preliminary conservation status are provided for C. nagaoi.
Keywords: Angiosperms, flora of Laos, Indochina, Malpighiales, taxonomy
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| Croton nagaoi Tagane, Soulad. & Souvann. A. branches; B. staminate flower with a bracteole; C. petals (outside); D. stamens, back view; E. stamen, front view; F. stamen, lateral view; G. fruit; H. seed. All from Tagane et al. L2459 (KAG [KAG128559]). Scale bars: A = 3 cm, B–F = 1 mm, G = 8 mm, H = 5 mm. Line drawing by K. Souvannakhoummane. |
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| Croton nagaoi Tagane, Soulad. & Souvann. A. Flowering branch; B. portion of abaxial leaf surface; C. base of leaf showing basal gland lateral on base of midrib; D. stellate hairs on lower leaf surface; E. inflorescence consisting of staminate flowers; F. staminate flower; G. petal of staminate flower; H. stamen; J. fruit; K. pistillate flower, lateral view, showing sepals and petals; L. petals of pistillate flower; M. stigma; N. seed. All from Tagane et al. L2459. Scale bars: D = 0.5 mm, G, H, L, M = 1 mm, N = 5 mm. Photographs by S. Tagane. |
Croton nagaoi Tagane, Soulad. & Souvann., sp. nov.
Most similar to Croton thorelii Gagnepain (1921: 560) of Laos, Cambodia, Thailand and Vietnam in size and shape of
lamina, short petioles less than 1 cm long, and basal glands lateral on the abaxial midrib base, but distinguished from
it by its lower leaf surface densely covered with persistent yellowish-cream stellate hairs (vs. very sparsely pubescent
and glabrescent in C. thorelii) (Fig. 4), and the presence of petals in pistillate flowers (vs. absence).
...
Etymology:—The species epithet is dedicated to the excellent Nagao Natural Environment Foundation (http://
www.nagaofoundation.or.jp/e/) that has promoted nature conservation in Asia-Pacific countries since its establishment
in 1989. Thanks to their support, we could have intensive field surveys on the Bolaven Plateau, which resulted in
a better understanding of the flora of Bolaven and the discovery of more than 18 new species including the new
species of Croton described in this study and 65 new country records (e.g. Souladeth et al. 2020, Tagane et al. 2020,
Souvannakhoummane et al. 2021, Vongthavone et al. 2021).
Vernacular name:— ເປົ້າດົງ Pao Dong (suggested here; ‘Pao’ refers to the genus Croton and ‘Dong’ refers to the
forest area).
Shuichiro Tagane, Keooudone Souvannakhoummane and Phetlasy Souladeth. 2022. Croton nagaoi, A New Species of Euphorbiaceae from southern Laos. Phytotaxa. 570(2); 102-108. DOI: 10.11646/phytotaxa.570.2.1
