Premna, Linnaeus, 1771

Tan, Yun-Hong, Min, Dao-Zhang, Ding, Hong-Bo, Yang, Bin, Maw, Mya Bhone & Li, Bo, 2021, Premna caridantha (Lamiaceae: Permnoideae), a distinct new species from Kachin State, northern Myanmar, Phytotaxa 490 (1), pp. 107-113 : 112

Key to the four species of Premna having spike-like inflorescences

1. The inflorescence is a single spike-like thyrse without branches; corolla tube straight and obviously much longer than calyx ........ .......................................................................................................................................................................................... P. interrupta

1. The inflorescence is a panicle formed by branches of spike-like thyrses; corolla tube straight or incurved, as long as calyx or slightly longer than calyx.

2. Tall trees; the axis of inflorescence has1–4 pairs of secondary branches ........................................................................ P. bracteata

2. Large woody climbers; the inflorescence intricate with 4–6 pairs of secondary branches and each secondary branch with 1–3 pairs of tertiary branches.

3. Leaf blade broadly ovate to subrounded; flowers nearly actinomorphic; corolla tube straight and extremely short; corolla without colorful spot; stamens radially exerted................................................................................................................. P. grandipaniculata

3. Leaf blade oblong to ovate; flowers strongly zygomorphic; corolla tube incurved, slightly longer than calyx; middle lob of the lower lip with a bright yellowish spot; stamens exerted under the upper lip ................................................................. P. caridantha