It's a buckeye, probably a California Buckeye (Aesculus californica).
On 10/19/12, Jan Lauritzen <firstname.lastname@example.org> wrote:
> Hi All,
> My daughter bought a house last June. We have been watching a tree produce
> what we, at first, thought was some kind of fruit. Then we thought it might
> be an almond but the leaves didn't look right. They have been getting
> bigger and bigger and now are splitting into 3 parts at the end of the
> fruit. Inside is something which, to me, looks like it resembles some kind
> of chestnut. However, we are in Southern California and I never even see
> Chestnuts except a few in the market in December.
> Would really like to know what we have. If you can help, thank you ahead of
> Jan in Chatsworth