Desert DiaryIdentifying plants often is no easy task. Oh sure, everyone can tell you if it's an oak or a pine (well, almost everyone). But what kind of oak, what kind of pine? To get things down to species, a vast jungle of terms has grown. Is a leaf margin entire, finely toothed, toothed, double-toothed, wavy margined, or deeply lobed? Is the leaf tip notched, broad and notched, long-pointed, tapering, or rounded? Is the base of the leaf blade asymmetrical, heart-shaped, squared, rounded, or narrow?
Now you might ask, "Who cares?" But if you need to identify plants, you care, because without knowing what these terms mean, you have little chance of correctly determining the
species of many plants. Identification usually is by way of keys: of alternate characteristics that lead to further alternatives. Mistake one feature for another, and you end up with egg on your
face. Of course, leaves are not the only structures considered. There are flowers, stem types, and lots more. If you were addicted to puns, you might say the variety is beyond be-leaf! 
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
A single leaf of the Golden-ball Lead Tree . The ancestral leaf blade has been divided and then each division divided again during its evolution.