An Ancestral Secret
When the rapid growing eucalyptus tree pushes out its leaves it discloses one of the secrets of its ancestry. Some of the leaves, like those at the top of the branch pictured above, are narrow and long. Others, lower down, are much broader. On a single tree it is common to find five or six different kinds of leaves seeming, when laid side by side, as though they must have come from separate plants. The history of the eucalyptus, as disclosed by its leaves, its quick growth, and other characteristics, is that one time it was an herb-perhaps an annual. To fit themselves to some new environment, its ancestors succeeded in establishing themselves as perennials. But this change was so recent that the evidence of the transition are still to be found in the leaves of all young eucalyptus trees today.
This image is from: Luther Burbank: his methods and discoveries and their practical application. Volume 1 Chapter 2