Monophyllaea horsfieldii is an herbaceous lithophyte belonging to the family Gesneriaceae and found mostly on limestone outcropings in Borneo and peninsular Malaysia.

The entire plant consists of a single cotyledon of Brobdingnagian proportions; the blade or lamina can be "over a metre" (over 40 inches) in length and about 30 inches (75 centimeters) wide, topping a massive hypocotyl of similar length.

It grows new tissue at the joint of the blade and hypocotyl, while the oldest tissue at the edge gradually dies back.

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