Fenestraria rhopalophylla subsp. aurantiaca

Fenestraria rhopalophylla subsp. aurantiaca is a dwarf mesemb, a succulent using windows but not those designed by Microsoft.

The plants grow in coastal sand, exposed to sun and wind in harsh semi-desert conditions. Their region receives about 100 mm of annual winter rain, augmented during periods of low fog rolling in from the sea. Extreme temperatures and sandstorm inducing winds render living conditions severe on plant and animal that make this land their home. What shape could optimise survival here?

The underground leaf bodies with windows on top conduct sunlight through their non-glass, plant skin windows. Light travels slower but surely down through the dense optical medium of transparent, water-storing tissue to unseen chlorophyll cells deep inside. This is where the underground plant “food factory” resides, supporting a weird but effective desert existence.

Such succulent leaf bodies, their true green, photosynthesising parts well hidden, have evolved in several flowering plant genera and many species of the arid regions. Examples in the Aizoaceae family include Fenestraria, Lithops and Conophytum.

Other genera like Bulbine and Haworthia have undergone the same adaptation independently, all examples of a phenomenon of evolutionary convergence, a process of similar response to similar environmental challenge, elicited from different genetic endowment.

A bit like great minds thinking alike when prodded by the same stimuli. Or when inventing the same solution when development has reached a certain point of new challenge, as Newton and Leibniz did in mathematics when simultaneously inventing calculus without conferring or comparing notes (Grenier, 2019; Frandsen, 2017; Williamson, 2010; Smith, et al, 1998).