Arisaema cordatum

Genus Arisaema Mart. (Araceae)
ca. 150 spp. distributed mainly in the tropical, subtropical and temperate region in Asia. About 82 spp. can be found in China in which 59 spp. are endemic to China. Most of the Arisaema is found in Yunnan province where 40 spp. are in Yunnan. 4 species are distributed in Hong Kong.

Arisaema has an unique and interesting inflorescence which is like a pitfall-trap system. Arisaema always form a spathe tube and a spadix appendage which probably attracts the pollinators. Pollinators landing on the apadix appendage slide to the bottom of the tube because ablative wax cover both the inner surface of the tube and the surface of the apadix appendage. Pollinators entering male flower are able to escape from the tube at the hole located at the bottom of the spathe tube while pollinators (maybe carrying pollen grains) entering female flower are trapped as no hole is formed at the bottom of the tube. They walk around to find an exit, while depositing pollen grains on the stigma.

Arisaema cordatum is endemic to China and can only be found in Guangdong and Guangxi provinces. It is narrowly distributed in Hong Kong where only two localities, Tai Mo Shan and Sunset Peak, are reported.

Marsdenia lachnostoma

Genus Marsdenia R. Br. (Asclepiadaceae)
ca. 100 spp. distributed in the tropical regions in America, Africa and Asia. 22 spp. are distributed in China while only 1 species, Marsdenia lachnostoma, is found in Hong Kong. Marsdenia are mostly climbers where shrubs or subshrubs are rare.

Marsdenia lachnostoma is a rare species in China and Hong Kong. Its range is so narrow that it is only distributed in Hong Kong within China (It is also found in Cambodia, Laos and Tailand). Because of this, it is listed in the rare and precious plants of Hong Kong and catergorized as critically endangered in the China Red Plant Data Book. Furthermore, it is still not a common species in Hong Kong while it can only be found in a few localities such as Ma On Shan, Tung Lung Chau and High Junk Peak.

The common name of M. lachnostoma is called Hairy-throat Condorvine. It is because the throat of its flowers is covered by a very dense tuft of woolly hairs.