In wet places in the Australian rainforest dwells Cyrtandra baileyi, a delicate relative of the African violet. This shrub which appears to be restricted to permanently wet places in rainforest, is endemic to the region and was first collected by botanist Frederick Manson Bailey.
At a first glance, one might interpret Cyrtandra to have alternate leaves, but closer inspection would reveal a rather strange feature – at each leaf node, there is pointed appendage opposite each leaf. Cyrtandra actually has opposite leaves, one of which is greatly reduced.
What came to my mind was a rather macabre analogy: Cyrtandra has a leaf with a “vanishing twin” – the phenomenon in animals where a fetus in a multi-gestation pregnancy which dies in utero and is then partially or completely reabsorbed by the twin.
Interestingly, there are other plants that do this, but that is another story for another time.