Trigonostemon laevigatus var. croceus, 2018

Yu, R. - Y. & Welzen, P. C. van, 2018, A taxonomic revision of Trigonostemon (Euphorbiaceae) in Malesia, Blumea 62 (3), pp. 179-229 : 197

b. var. croceus (B.C.Stone) R.Y.Yu & Welzen , comb. nov. & stat. nov. — Map 5

Trigonostemon croceus B.C. Stone (1980) 249. — Type: Stone 9586 (holo KLU; iso K, L, PH*), Malaysia, Selangor, on the Pahang border at Genting Sempah .

Sepals with a gland outside.

Distribution — Thailand, Malay Peninsula.

Habitat & Ecology — Hill evergreen forest to grassy sites. Altitude: 900–1300 m. Flowering: November to May.

Note — Stone (1980) newly described T. croceus , because it had 5 instead of the 3 stamens of T. laevigatus . We dissected one staminate flower from the isotype and it turned out to have 3 stamens. Its only difference from the typical T. laevigatus are the showy, protruding glands on the sepals, but there is a continuous variation from being glandless to having a flat gland to even having a protruding gland. However, according to the specimen notes the croceus form occurs at higher altitudes than the typical laevigatus form. Therefore, T. croceus is here regarded as a variety of T. laevigatus .