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.
References
<p align="justify"><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: small;">Esser, H.-J. (2005) <em>Croton.</em> <em>In</em>: Chayamarit, K. & van Welzen, P.C. (eds.) <em>Flora of Thailand 8 (1), Euphorbiaceae (Genera A–F)</em>. The Forest Herbarium, Bangkok, pp. 189–226<em>.</em></span></span></span></p>
<p align="justify"><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: small;">Esser, H.-J. (2010) <em>Croton fluviatilis </em>(Euphorbiaceae), a new species from Thailand. <em>Thai Forest Bulletin (Botany)</em> 38: 33–36. [https://li01.tci-thaijo.org/index.php/ThaiForestBulletin/article/view/24342]</span></span></span></p>
<p align="justify"><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: small;">Forster, P.I. (2003) A taxonomic revision of <em>Croton</em> L. (Euphorbiaceae) in Australia. <em>Austrobaileya</em> 6: 349–436. https://www.jstor.org/stable/41738992</span></span></span></p>
<p align="justify"><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: small;">Gagnepain, F. (1921) Euphorbiacees nouvelles d’Indo-China (<em>Croton</em>). <em>Bulletin de la Société Botanique de France</em> 68: 548–562. https://doi.org/10.1080/00378941.1921.10836236</span></span></span></p>
<p align="justify"><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: small;">Gagnepain, F. & Beille, L. (1925) Euphorbiacées<em>.</em> <em>In:</em> Lecomte, P. H & Gagnepain, F. (eds.) <em>Flore Générale de l’Indo-Chine</em> 5. Masson, Paris, pp. 229–673.</span></span></span></p>
<p align="justify"><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: small;">Govaerts, R., Frodin, D.G. & Radcliffe-Smith, A. (2000) <em>World Checklist and Bibliography of Euphorbiaceae (and Pandaceae) </em>1–4. Royal Botanic Gardens, Kew, 1621 pp.</span></span></span></p>
<p align="justify"><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: small;">Hô, P.H. (2003) <em>Cây Cỏ Việt Nam: An Illustrated Flora of Vietnam</em> 2. Published by the author, Montreal, 951 pp.</span></span></span></p>
<p align="justify"><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: small;">IUCN (2012) <em>IUCN Red List Categories and Criteria: version 3.1, second edition</em>. IUCN, Gland and Cambridge, 32 pp.</span></span></span></p>
<p align="justify"><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: small;">Li, P.T. & Esser, H.-J. (2008) <em>Croton</em>.<em> In</em>: Wu, Z.Y., Raven, P.H. & Hong, D.Y. (eds.) <em>Flora of China</em> 11. Missouri Botanical Garden Press, St. Louis and Science Press, Beijing, pp. 258–264. Available from: http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=108445 (accessed 15 October 2021).</span></span></span></p>
<p align="justify"><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: small;">Linnaeus, C. (1753) <em>Species Plantarum</em>. L.Salvius, Stockholm, 1200 pp.</span></span></span></p>
<p align="justify"><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: small;">Newman, M.F., Thomas, P., Lanorsavanh, S., Ketphanh, S.K., Svengsuka, B. & Lamxay, V. (2007) New records of angiosperms and pteridophytes in the flora of Laos. <em>Edinburgh Journal of Botany </em>64: 222–251. https://doi.org/10.1017/S0960428607000923</span></span></span></p>
<p align="justify"><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: small;">Newman, M.F., Pullan, M., Ketphanh, S., Svengsuksa, B., Thomas, P., Sengdala, K., Lamxay, V. & Armstrong, K. (2017–present) <em>A Checklist of the Vascular Plants of Lao PDR</em>. Online database available at https://padme.rbge.org.uk/laos/ (accessed 1 October 2022).</span></span></span></p>
<p align="justify"><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: small;">Souladeth, P., Tagane, S., Newman, M.F. & Prajaksood, A. (2020) Two new species of <em>Eriocaulon</em> (Eriocaulaceae) from Laos. <em>Kew Bulletin</em> 75: Article number 56. https://doi.org/10.1007/S12225-020-09909-0</span></span></span></p>
<p align="justify"><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: small;">Souvannakhoummane, K., Lanorsavanh, S., Tagane, S., Souladeth, P., Phonpaseuth, P., Pongamornkul, W. & Lamxay, V. (2021) Six new species and eight new records of Gesneriaceae from Laos. <em>Gardens’ Bulletin Singapore</em> 73: 427–456. https://doi.org/10.26492/gbs73(2).2021-13</span></span></span></p>
<p align="justify"><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: small;">Tagane, S., Toyama, H., Chhang, P., Nagamasu, H. & Yahara, T. (2015) Flora of Bokor National Park, Cambodia I: Thirteen new species and one change in status. <em>Acta Phytotaxonomica et Geobotanica </em>66: 95–135. https://doi.org/10.18942/apg.KJ00010001424</span></span></span></p>
<p align="justify"><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: small;">Tagane, S., Souladeth, P., Rueangruea, S., Okabe, N., Zhang, M., Chayer, S., Yang, C.-J. & Yahara, T. (2018) Flora of Nam Kading National Protected Area II: 30 new records of angiosperms for Laos. <em>Edinburgh Journal of Botany </em>75: 107–116. https://doi.org/10.1017/S0960428617000361</span></span></span></p>
<p align="justify"><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: small;">Tagane, S., Souladeth, P., Kongxaysavath, P., Rueangurea, S., Suddee, S., Suyama, Y., Suzuki, E. & Yahara, T. (2020) Two new species and 18 new recrods for the for a of Laos. <em>Thai Forest Bulletin (Botany)</em> 49: 111–126. https://doi.org/10.20531/tfb.2021.49.1.14</span></span></span></p>
<p align="justify"><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: small;">Thin, N.N. (2007) <em>Taxonomy of Euphorbiaceae in Vietnam</em>. Vietnam National University Publishers, Hanoi, 407 pp.</span></span></span></p>
<p align="justify"><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: small;">Vongthavone, T., Tagane, S., Phonepaseuth, P., Souvannakhoummane, K. & Souladeth, P. (2021) Twelve new records of pteridophytes from Bolaven Plateau, southern Laos. <em>Thai Forest Bulletin (Botany) </em>49: 182–190. https://doi.org/10.20531/tfb.2021.49.2.05</span></span></span></p>
<p align="justify"><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: small;">Webster, G.L. (1993) A provisional synopsis of the sections of the genus <em>Croton</em> (Euphorbiaceae). <em>Taxon</em> 42: 793–823. https://doi.org/10.2307/1223265</span></span></span></p>
<p align="justify"><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: small;">WCSP (2022) <em>World Checklist of selected plant families</em>. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet; available at http://wcsp.science.kew.org/ (accessed 3 March 2022).</span></span></span></p>
<p align="justify"><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: small;">Whitmore, T.C. (1972) Euphorbiaceae.<em> In:</em> Whitmore, T.C. (Ed.) <em>Tree Flora of Malaya</em> 2. Longman, Kuala Lumpur, pp. 34–136.</span></span></span></p>