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Hydrocotyle L.
Mark F. Watson
Royal Botanic Garden Edinburgh

Prostrate herbs; stems usually rooting at nodes. Leaves simple, suborbicular in outline, usually lobed and base deeply cordate;  petioles not sheathing, but with small, broadly ovate, membranous stipules. Umbels small and densely clustered, simple; bracts and bracteoles absent or minute. Calyx teeth minute or obsolete. Petals entire, small. Stylopodium domed. Fruit orbicular, laterally compressed, glabrous, mericarps keeled on the back but lateral primary ribs weak. 

Key to species
1 Leaves up to 1.5cm across, glabrous on upper surface; umbels 2–3mm diameter H. sibthorpioides
+ Leaves >2cm across, usually pubescent on upper surface with thick hairs; umbels 4–15mm diameter 2
2 Leaves round in outline; umbels always solitary; fruiting pedicels >2mm H. himalaica
+ Leaves somewhat angular in outline; umbels usually several in leaf axils; fruiting pedicels <2mm H. nepalensis

Hydrocotyle himalaica P.K.Mukherjee
    Hydrocotyle javanica Thunberg var podantha C.B.Clarke non Molkenboer
    Hydrocotyle podantha auct. non Molkenboer
Vernacular Name: Ghora Tophay (Nepali) 

Stems sparsely brown pubescent. Leaves orbicular in outline with 5–7 broad, shallow, very rounded lobes, (0.8–)1.5–3(–6) x 1.2–8cm, margins crenate-dentate, sparsely strigose pubescent on both surfaces; petioles 1–18cm, densely pubescent near apex. Umbels solitary in leaf axils, to 13mm across in fruit; peduncles 1.5–10cm, usually as long or longer than the petioles of the subtending upper leaves; pedicels (2–)4–7mm in fruit. Petals narrowly triangular greenish cream, 1–1.3mm, slightly incurved at apex. Styles persistent, spreading in fruit (0.6–)0.8–1mm long. Fruit c 1 x 1.5mm. 

Bhutan: S—Chukka district (Chukka Bridge) and Deothang district (Keri Gompa); C—Mongar district (Tashigang to Mongar); N—Upper Kuru Chu district (Denchung).
Sikkim: Bitu, Gangtok, Karponang, Labdah, Penlang La, Yoksam.
Darjeeling: Chunabate, Darjeeling, Kurseong, Mungpoo, Senchal. 

Ecology: Damp shady areas, banks in forests, streamsides, etc. 1500–2450m.
Flowers April–September. 

Illustration[ Fig 48 a–d]

Specimen List [7593]

Distribution Map for Hydrocotyle himalaica P.K.Mukh. in the East Himalayan Region
[complete records for Bhutan, Chumbi, Sikkim and Darjeeling, partial data for East Nepal]

Hydrocotyle nepalensis Hook.f.
    Hydrocotyle hispida D.Don
    Hydrocotyle javanica sensu F.B.I. pp.
    Hydrocotyle polycephala Wight & Arnott
Similar to H. himalaica in habit, but differing in leaf shape, umbel form, most noticeably in fruit. Leaves anglular in outline, lobes usually triangular, 2–9 x 2.8–11cm, strigose hairs rather longer than H. himalaica and thus appearing coarser. Umbels often in clusters of 2–9(–12) at nodes, seldom solitary, 4–7mm across in fruit; peduncles 0.5–4cm, shorter than the subtending petiole; pedicels 0.5–1.5(–2)mm in fruit. Styles spreading to erect in fruit, 0.3–0.5mm. 

Bhutan: S—Chukka district (Chukka, Chukka Bridge), Deothang district (Samdrup Jongkhar) and Gaylegphug district (Aie Bridge, Gaylegphug to Shemgang) districts; C—Punakha district (Lobesa to Lomentsawa, Shenganga) and Mongar district (Shongar).
Sikkim: Badamtan, Damthang–Temi, Gangtok, Hi, Pemayangtse–Thingling, Rimbi, Sirong.
Darjeeling: Birch Hill, Ghum, Kali, Kalimpong, Lebong, Senchal, Takvar. 

Ecology: Damp shady areas, banks in forests, streamsides, etc. 500–2500m.
Flowers May–July. 

Specimen List [7482]

Note: This species and H. himalaica are very closely related and poorly understood. They, and the other members of the H. javanica complex need further study on a worldwide scale. 

Hydrocotyle sibthorpioides Lamarck
    Hydrocotyle rotundifolia DC.
    Hydrocotyle tenella D.Don
Similar to H. himalaica and H. nepalensis, but much smaller, with slender, filiform stems; leaves with rounded lobes, 7–11 x 9–15mm, glabrous above, glabrous or sometimes pubescent beneath; petioles 1–6cm, filiform; stipules rather conspicuous; umbels 2–3mm across in fruit, usually subsessile or on peduncles up to 2(–3)cm; pedicels 0–0.5mm; fruit c 1 x 1.2mm. 

Bhutan: S—Samchi district (Daina Khola) and Gaylegphug district (Norbuling); C—Thimphu district (Simtokha–Dochu La), Punakha district (Punakha Dzong) and Tongsa district (Tongsa).
Darjeeling: Birik, Char Churabhandar, Siliguri, Takdah. 

Ecology: Damp shady areas, banks in forests, streamsides, etc. 300–2350m.
Flowers March–May. 

Specimen List [7533]

Note: Plants with leaves pubescent below may be distinguished as forma pilosa Hara. 

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