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Pternopetalum Franchet
Mark F. Watson
Royal Botanic Garden Edinburgh

Bhutanese representatives are essentially glabrous, slender little-branched annuals with short fusiform tap-roots. Leaves biternate or pinnatisect; petioles slender with ovate sheathing bases. Umbels compound, mainly terminal; rays somewhat unequal; bracts absent; umbellules 2–3-flowered; pedicels very short and conspicuously unequal; bracteoles present, linear. Calyx teeth minute triangular. Petals white to purplish, ovate, acute spreading or incurved. Stylopodium domed. Fruit ovoid-ellipsoid, slightly compressed laterally, mericarps weakly ribbed, smooth. 
Key to species
1 Leaves biternate; leaflets serrate at apex; rays not filiform P. radiatum
+ Leaves pinnate with (1-)2–4 pairs of leaflets; leaflets 3-lobed, often deeply so; rays filiform P. subalpinum

Pternopetalum radiatum (W.W.Smith) P.K.Mukherjee
    Pimpinella radiata W.W.Smith
    Acronema radiatum (W.W.Smith) H.Wolff
    Pternopetalum delicatulum (H.Wolff) Handel-Mazzetti
Stems 12–55cm. Leaves 2–8 x 1.5–4.5cm (including petiole), triangular-ovate in outline, biternate; ultimate segments 5–16 x 5–10(–15)mm, ovate-elliptic, apex acute, base cuneate, margin serrate in upper half, glabrous except margins and main veins with sparse stiff hairs; upper stem leaves narrower and more deeply incised; petioles 1.5–5cm. Umbels c 3cm across, mainly terminal with 0–2 smaller laterals, (5-)8–12(-14)-rayed; rays 0.5–2.5cm; umbellules 2–3-flowered; pedicels 0–2mm; bracteoles 1–2, 1–2mm. Petals greenish-white sometimes purple margined. Stylopodium green; styles purple, recurved. Fruits 1.5–2 x 1.3–1.5mm. 

Bhutan: C—Bumthang district (Lami Gompa) and Thimphu district (Dotena to Barshong, Hongsto); N—Upper Kuru Chu district (Julu).
Sikkim: Yumthang. 

Ecology: Damp shaded banks in hemlock and fir forests, 3100–3400m. Flowers June–July. 

Illustration [Fig. 51 l,m]

Specimen List [12141]

Pternopetalum subalpinum Handel-Mazzetti

Delicate unbranched herb, 5–10(-20)cm tall. Leaves almost entirely basal, 3–8 x 0.6–1.5cm (including petiole), pinnate with (1-)2–4 pairs of leaflets; leaflets broadly ovate, 2.5–7 x 1.5–8mm, acutely 3-lobed, often deeply so, almost glabrous; petiole 3–5cm. Umbels entirely terminal, 5–10-rayed; rays 1.5–3.5cm, filiform, unequal; umbellules mostly 2–flowered; pedicels 0.2–2mm; bracteoles 2, 0.75–1.5mm. Petals white to purplish. Styles purple. Fruits c 1.5 x 0.75mm. 

Bhutan: C—Tongsa district (Yuto La); N—Upper Mo Chu district (Kohina) and Upper Kulong Chu district (Lao).
Sikkim: Tsoka to Jamlinghang. 

Ecology: Shaded mossy banks and rocks in fir forests, 3000–3550m. Flowers June-July. 

Specimen List [12104]

Note: Literature references to P. tanakae (Franchet & Savatier) Handel-Mazzetti occuring in Bhutan are based on a misidentifed specimen of P. subalpinum.

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