California buckeye is endemic to the state. Its poisonous properties were recognized and utilized by the First Nations of the region, who ground the seeds into flour and then used the flour as a fish poison (ref: Jepson Manual and expanded in the Wikipedia entry on Aesculus californica).
Henry W. Coe State Park shares a series of photographs of California buckeye on its web site, if you’re keen to see the plant from other perspectives and in detail.
On a different note, if you live in the Seattle area, you might like to attend my lecture on “Beauty and the Botanist” at 1pm tomorrow at the Centre for Urban Horticulture (3501 NE 41st St.), hosted by the Northwest Perennial Alliance. Cost is $5 if you’re not an NPA member.
Botany / art resource link: Discovered via Pruned weblog, Wood Anatomy of Central European Species shows the beauty of wood at the cellular level. Take a look at Larix decidua as a fine example of what’s available in the list of species.