Pilea rivularis Wedd.

Urticaceae, I. Friis University of Copenhagen, Denmark. Flora of Tropical East Africa. 1989

Morphology General Habit

Perennial herb with prostrate and ascending stems, up to 1 m. high; apparently mostly dioecious, or at least each shoot unisexual.

Morphology Stem

Stems little branched, often ± lignified at base, glabrous, with linear cystoliths and occasionally reddish or orange glands in epidermis.

Morphology Leaves

Leaves of a pair subequal or equal; stipules large and prominent, persistent, circular, oblong or ovate, 6–10 mm. long, 4–8 mm. wide, transparent, with subcordate base and rounded apex; petiole extremely variable, 0.4–5(–8.5) cm. long, glabrous or with a few hairs at connection with lamina; lamina ovate to lanceolate, 0.5–8(–10.5) cm. long, 0.5–3.5(–6) cm. wide, base cuneate to truncate or subcordate, margin crenulate to serrate, with 4–15(–20) teeth on each side, apex acute to long acuminate; lateral nerves 3–4 pairs, basal pair reaching ± 2/3 of the way to the apex before joining with the upper lateral nerves and arching towards the midnerve; both upper and lower surface with dense linear cystoliths, on the nerves of the lower surface often a ± dense indumentum of spreading hairs.

Morphology Reproductive morphology Inflorescences

Inflorescences sessile, dense glomerules, up to 1(–1.3) cm. in diameter, mostly unisexual, rarely with a few flowers of the opposite sex intermixed, single in the upper leaf-axils, with small linear bracts between the flowers.

sex Male

Male flowers 3-merous, on pedicels l–2.5(–4) mm. long; perianth globular to ovoid, ± 2 mm. long (not including appendages); tepals equal, with prominent linear cystoliths in epidermis, each with a subapical filiform appendage 0.8–1.5 mm. long.

Morphology Reproductive morphology Flowers

Female flowers on pedicels 1–2 mm. long; perianth 1–1.5 mm. long, divided almost to the base, with 3 ovate, subequal lobes, the middle one with a subapical appendage up to 0.5 mm. long, lateral lobes 2/3–4/5 as long as the middle lobe, usually also with a ± developed subapical appendage; staminodal scales about as long as perianth-segments. Male flowers 3-merous, on pedicels l–2.5(–4) mm. long; perianth globular to ovoid, ± 2 mm. long (not including appendages); tepals equal, with prominent linear cystoliths in epidermis, each with a subapical filiform appendage 0.8–1.5 mm. long.

sex Female

Female flowers on pedicels 1–2 mm. long; perianth 1–1.5 mm. long, divided almost to the base, with 3 ovate, subequal lobes, the middle one with a subapical appendage up to 0.5 mm. long, lateral lobes 2/3–4/5 as long as the middle lobe, usually also with a ± developed subapical appendage; staminodal scales about as long as perianth-segments.

Morphology Reproductive morphology Fruits

Achene brown to pale brown or whitish, ovoid, 1.5–2.5 mm. long, 1–1.5 mm. wide, ovoid, compressed, occasionally with a flat, marginal wing (rarely the wing dissolved into hooked bristles).

Figures

Fig. 8/F–J.

Habitat

Along streams and in other moist places in upland rain-forest or montane forest; 1250–3100 m.

Distribution

K3 K4 K5 K6 K7 T2 T4 T6 T7 T8 U1 U2 U3

Urticaceae, I. Friis. Flora Zambesiaca 9:6. 1991

Morphology General Habit

Perennial herbs with creeping rhizomes and erect, mostly unbranched stems up to 0.5(1) m. tall, dioecious or at least each shoot unisexual.

Morphology Leaves

Leaves of a pair subequal or equal, 2–5(10) x 1.5–3.5(6) cm., broadly ovate to ovate-lanceolate, apex acuminate; base obtuse, truncate or rounded, rarely subcordate; margin serrate or dentate with 5–15(20) teeth per side; glabrous on both sides with dense linear cystoliths.

Morphology Leaves Petiole

Petiole 4–6 cm. long.

Morphology Leaves Stipules

Stipules up to 0.5 cm. long, broadly ovate, base often cordate or almost amplexicaul.

Morphology Reproductive morphology Inflorescences

Inflorescences of dense uni- or bisexual clusters in the leaf axils, distributed along the stems.

Morphology Reproductive morphology Flowers

Male and female flowers on pedicels up to 2 mm. long, 3-merous, tepals with a very prominent horn-like appendage; stigma penicillate.

sex Male

Male and female flowers on pedicels up to 2 mm. long, 3-merous, tepals with a very prominent horn-like appendage; stigma penicillate.

Morphology Reproductive morphology Fruits

Achene c. 2 mm. long, ovoid, compressed, smooth.