Acampe rigida

Illustration of Acampe rigida as Vanda multiflora from Lindley, John: Collectanea Botanica (1821)

Acampe rigida is a robust species with an unbranched stem up to 1 m (40 in) in length and 20 mm (0.8 in) in diameter. The leaves are distichous. The stem nodes are about 25 mm (1 in) apart and each bears a somewhat fleshy, upright leaf with sheathing base. The apices of the leaves are obtuse and unequally bilobed. The inflorescence is unbranched or sparsely branched, with many slightly fragrant, upturned, cup-shaped flowers less than 25 mm (1 in) in diameter. The petals are fleshy, and are yellow with purplish-brown stripes; they have a thick, white, three-lobed lower lip, and a short spur. They are followed by cylindrical or fusiform capsules.[2]

Acampe rigida is native to the Andaman Islands, Assam, Bangladesh, Bhutan, Cambodia, China, India, Laos, Malaysia, Myanmar, Nepal, the Philippines, Sri Lanka, Thailand and Vietnam.[1][2] It occurs in forests, either growing epiphytically on the branches and trunks of trees, or growing on rocks, and often forming dense clumps. Its altitudinal range is from 300 to 1,800 m (1,000 to 6,000 ft).[2]

Acampe rigida is a deceptive orchid in that it produces a fragrance that may attract insects but does not then offer them any reward. It is self-compatible, but has not evolved any particular mechanism to enable self-pollination. In Guangxi province in southwestern China, it flowers in late August and September, at a time of year when rain falls almost daily and insect pollinators are scarce. In a research study, after many hours of observation, a single insect was observed to visit a flower, but pollination did not occur. Instead, the plant exhibited ombrophily; rain drops falling on the tips of the stamens knocked the caps off the anthers, and further drops caused the pollinia to be ejected upwards, after which strap-like stipes arrested their movement and caused them to land in the stigma cavity, resulting in self-pollination. A high rate of fruit set occurred, but without the action of the raindrops, self-pollination did not occur and fruit did not set.[3]

• Media related to Acampe rigida at Wikimedia Commons
• Data related to Acampe rigida at Wikispecies