I found a plant growing wild in So. Cal. The early part of the growth, the lower section of the plant had regular leaves, but the upper part had apparently abandoned the leaves and the stems had grown frills, or something; raised sections along each part of the stem on either side, flat and about 1/2 inches wide.
My guess water that it changed to this form of growth to conserve water.
there is probably a name for this type growth and for this plant, I know neither.