Leaves a bit variable but mostly oblong (longer than wide, but with parallel or flattened margins in the middle of the leaf), sometimes obovate (egg-shaped but with the widest part toward the tip) or even round (orbicular). Leaves are mucronate (with a small tip). Leaves narrow at the base to a very short petiole. Leaves ~2-9 cm long and are well separated from one another, giving a scattered appearance. They are pale green on both surfaces. Stems are stout, glabrous (smooth-surfaced), and grey-brown, while the branchlets are rather thorny. The inflorescence consists of solitary flowers, which may have leaf-like bracts on their peduncles (flower stalks). There are usually 5 sepals (though there may be anywhere from 3-6 of them) ~ 1 cm long and round to ovate in shape. There are usually 5 petals (again, variable, 3-6), which are white, rounded in shape, ~1.2-1.5 cm long, with wavy or fluted margins and often curving back over the sepals and peduncle. There are 15-50 stamens with bright yellow anthers (pollen-bearing structures), arranged in several series surrounding 1-9 pistils. The flower is, thus, rather conspicuous. Blooms from January through June. Produces 1-9 fruits, cylindrical in shape, ~0.8-2 cm long, which crack open to release 2 black and shiny round or flat seeds with a conspicuous fringed yellowish aril (or seed attachment). Plant itself is a shrub, sometimes tree-like, ranging from 1-5 m in height. It is drought-deciduous, so it may look pretty bare in summer. Favors dry rocky slopes and canyons under 500 m. Plant was believed confined strictly to Catalina Island, San Clemente Island, and (in Mexico) Isla Guadalupe until it was identified on Palos Verdes Peninsula in the Forrestal Preserve area. This is a rare and endangered species.
Crossosoma californicum (Crossosomataceae): Catalina crossosoma or California rockflower
The development of this key was partially funded through the Geoscience Diversity Enhancement Program (Award #0703798) and through a course of re-assigned time provided by the CSULB Scholarly and Creative Activities Committee. Thanks also to the students in sections of biogeography, introductory physical geography, GDEP, and LSAMP for "test-driving" various editions of this key.