Zingiber oligophyllum, K. Schum. A. Inflorescence, 1904

Bai, Lin, Leong-Škorničková, Jana, Xia, Nian-He & Ye, Yu-Shi, 2016, Taxonomic studies on Zingiber (Zingiberaceae) in China III: Z. ventricosum, a new species from Yunnan, and notes on three closely related species, Phytotaxa 261 (2), pp. 101-120 : 118

Key to the four species of the informal “ Z. oligophyllum complex”

1. Bracts densely imbricate, forming a compacted spike, rachis not visible at flowering....................................................................2.

- Bracts loosely arranged, forming a rather open spike, rachis often visible at flowering (or at least easily accessible by simply spreading the bracts)..........................................................................................................................................................................3.

2. Peduncles 12–25(–45) cm long, erect; bracts deeply convex with inflated base (forming prominently bullate spikes) and acuminate, wide-spreading apices; rhizomes tough, fibrous, well-elongated, creeping; distribution: China (Yunnan Province) ........................ ..................................................................................................................................................................................... Z. ventricosum

- Peduncles 1–5(–12) cm long, procumbent; bracts with no basal inflation (forming narrowly ovate spikes with smooth on surface), obtuse to acute or attenuate apices (not spreading); rhizomes fleshy, compacted, and densely branched; distribution: China (Yunnan Province), northern Laos, Thailand.............................................................................................................. Z. xishuangbannaense

3. Lateral staminodes narrowly oblong or spathulate, connate to labellum in the basal ca. 1/3, labella and lateral staminodes pale yellow to yellow; corolla lobes pale yellow, filament present; rhizomes compacted; distribution: mainland China (Guangdong, Fujian), Hong Kong and Taiwan) ............................................................................................................................. Z. oligophyllum

- Lateral staminodes asymmetrically obovate, connate to labellum in the basal 3/4, labella and lateral staminodes cream-yellow, often mottled with pale pink or pale purple; corolla lobes heavily tinged with red, filament absent; rhizomes elongated, almost creeping; distribution: southern Laos, southern Vietnam.................................................................................................. Z. thorelii