What is the fine-grained topic of the following text: Leaves 5–15 cm long; leaflets 2 or sometimes 4, opposite, elliptic to obovate, 4–10 cm long, 2–5 cm wide, apex acute or obtuse, base ± obtuse to attenuate, margins entire, both surfaces glabrous; reticulum fine, prominently raised in dried leaves; 1–3 prominent domatia on most leaflets; petiole 1–4 cm long, petiolules 5–10 mm long. Only return the topic.
Leaf morphology