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 33 compound to simple DHJanzen100344.jpg high resolution
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| In the cecropia tree above the leaflets are fixed in place within the leaf by not even being fully separate leaflets, but rather narrow lobes. Another way to achieve this is to have truly independent leaflets, but hold them rigidly in place (for the moment) in such a manner that they do not interfere with each other, as with this Mimosa albida shrub in Costa Rica. In the leaf in the lower left, you see six leaflets. However, in fact, the leaf is divided into four leafets, and each of THOSE is divided into two. Then, each of the two basal leaflets has reduced one of its leaflets to a tiny one, the two of which then fill the hole in the center (see high resolution image). The ancestors of this plant, living in desert habitats, had a compound leaf like the one that you know from the ant-acacia. However, as it has moved out of dryness (where a very highly subdivided leaf assists in keeping the leaf cool at high desert temperatures) into the more moist dry forest edges where Mimosa alba occurs, it is essentially reinventing a large single non-compound leaf by reducing the number of leaflets, making each remaining one large, and very carefully positioning them into what is functioning almost as a simple (single) leaf. | ||
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