王文採院士發現了自雲南東南部發現的蕁麻科樓梯草屬一新種，南溪樓梯草，此種與田林樓梯草(E. tianlinense)相似，但其葉具三出脈，邊緣具淺圓齒或小鈍齒，雄總苞苞片較少，8枚，排成一層，背面有1–3條縱肋，只1枚在頂端具角狀突起而與後者相區別。此外，此種與盤託樓梯草系的廣布種盤託樓梯草(E. dissectum)的區別在於其莖被糙伏毛，葉呈橢圓形，具三出脈，雄頭狀花序的花序梗較短，雄總苞苞片較少，呈寬卵形或橫長方形，背面有1–3條縱肋，雄小苞片有緣毛。
南溪樓梯草 圖1
Elatostema nanxiense W. T. Wang & Zeng Y. Wu, sp.nov. Fig. 1.
(Sect. Elatostemaser. Dissecta W. T. Wang)
Ob pedunculos capitulorum staminatorum quamreceptacula leviter longiores et receptacula late rectangularia species novahaec est similis E. tianlinense W. T.Wang, a quo foliis margine crenatis vel obtuse denticulatis trinervibus,bracteis involucralibus staminatis paucioribus 8 1-seriatis tantum singularibusapice corniculatis differt; in E.tianlnensi, folia margine acute dentata, semi-triplinervia, et bracteaeinvolucrales staminatae multiores ca. 20, 2-seriatae, 6 externae omnes apicecorniculatae sunt. Etiam ab E. dissecto Wedd., quod una species late distributa in Sect. Elatostema ser. Dissectis W. T. Wang est, caulibus strigillosis, foliis elliptcis
圖1 南溪樓梯草 A. 開花植株上部，B. 雄頭狀花序，下面觀，C,D.二對生長較大雄總苞苞片，E.雄花及4雄小苞片。
Figure1. Elatostema nanxiense A. upperpart of flowering stem, B. staminate capitulum, seen from beneath C,D. two opposite larger staminate bracts, E.staminate flower and four staminate bracteoles (from holotype)
trinervibus ventre ad nervos basalesstrigillosis, capitulis staminatis brevius pedunculatis (pedunculis 1–1.8 cm longis), bracteis involucralibusstaminatis paucioribus 8 late ovatis vel transverse rectangularibus dorsolongitudinaliter 1–3-costatis, bracteolis staminatis superne ciliatis facelerecedit; in E. dissecto, caulesglabri, folia oblique oblonga semi-triplinervia glabra, capitula staminata saepelonge pedunculata (pedunculi 1.5–8 cmlongi), bracteae involucrales staminatae saepe multiores lineares vel angustelanceolatae omnes haud costatae, bracteolae staminatae glabrae sunt.
Perennial herbs.Stem ca. 25 cm tall, below ca. 2.5 mm in diam., strigillose, simple, ca. 6-leaved. Leavesalternate; blades papery, obliquely elliptic, 11–13.5 × 4.2–5.8 cm, apex acuminate, base obliquelyand broadly cuneate, margin crenate or obtusely denticualte; surfaces adaxiallyglabrous, abaxially on basal nerves strigillose; nervation trinerved, withbasal nerves adaxially flat and abaxially slightly prominent, and with twopairs of secondary nerves; cysoliths numerous, dense, bacilliform, 0.25–0.5 mm long; petioles 1–3 mm long; stipules papery, broadly tonarrowly triangular, 4–4.2 × 1.2–2.2 mm, glabrous, at apex acute, greenish and with whitish margins.Staminate capitula singly axillary, pedunculate; peduncles 1–1.8 cm long, glabrous or with a fewshort hairs; receptacles broadly rectangular, obscurely bilobulate, 8–10 × 4–5.5 mm, glabrous; involucral bracts 8,1-seriate, membranous, glabrous, rarely on ribes with sparse short hairs, 2opposite bracts larger, very broadly ovate, 3–4 × 5–7 mm, abaxially longitudinally 2–3-ribbed, in thelargest bract, abaxially 3-ribbed and the apex of the central rib protrudingout to form a horn-like projection ca. 0.6 mm long, the 2 pairs of the lateral bracts transverselyrectangular, 3.2 × 4–5 mm,all abaxially longitudinally 1-ribbed and not corniculate; bracteoles numerous,very dense, membranous, white, linear, narrowly linear, or linear-oblanceolate,1–2.2 × 0.2–1.8 mm,above and on apex ciliate. Staminate flowers numerous, very dense, pedicellate;pedicels 0.3–1 mmlong, subglabrous; tepals 4, membranous, white, broadly triangular, 1 × 0.5 mm, apex acute, ciliate; stamens 4,glabrous, with very short filaments, anthers yellowish, oblong, ca. 0.8 mm long; pistillode absent.Pistillate capitula and pistillate flowers unknown.
雲南(Yunnan)：河口縣，南溪鎮，馬革，白沙河(Hekou Xian, Nanxi Zhen, Mage, Baisha River), alt. 388 m，河邊雨林裡路邊 (at road-side in rain forest near river)， 2010-08-01，吳增源 (Zeng Y. Wu) 10171 (♂, holotype, PE).
本種的雄頭狀花序的花序梗比花序託稍長，雄花序託寬長方形，因此，與也具上述特徵的田林樓梯草(E. tianlinense W.T. Wang) 相似，與後者的區別在於本種的葉在邊緣具淺圓齒或小鈍齒，具三出脈，雄總苞苞片數目較少，8枚，排成一層，只1枚在頂端具角狀突起；在田林樓梯草，葉在邊緣具尖牙齒，具半離基三出脈，雄總苞苞片數目較多，約20枚，排成二層，外層6枚均在頂端具角狀突起。本種與驟尖樓梯草組盤託樓梯草系 (Sect. Elatostema ser. dissecta W. T. Wang) 中的廣布種盤託樓梯草系 (E. dissectum Wedd.) 的區別在於本種的莖被短糙伏毛，葉呈橢圓形，具三出脈，下面基出脈上被短糙伏毛，雄頭狀花序的花序梗較短，長1–1.8 cm，雄總苞苞片較少，8枚，寬卵形或橫長方形，背面具1–3條縱肋，雄小苞片上部被緣毛；在盤託樓梯草，莖無毛，葉斜長圓形，具半離基三出脈，無毛，雄頭狀花序的花序梗多較長，長1.5–8 cm，雄總苞苞片常較多，呈條形或狹披針形，無肋，雄小苞片無毛。(王文採，2014)