In the photo of the seedlings, the leaves appear to have short petioles. In the photo of the leaves themselves I don't see petioles and they appear to have been sessile, so can you verify if there are petioles or not? Im not familiar with California plants, but is there any chance it could be Laurus nobilis, Bay Laurel?

The leaf comparison is one leaf from one of the seedlings and one leaf from the tree. I assumed the seedlings were from the tree right next to it but the leaves look different. The fruit is probably from the tree or maybe from the palms nearby.

Is one of the leaves turned over, or is that photo showing the upper side of both?

The seedlings look very different from the 2 leaves photo as well. Are the leaf stems severed?

Both leaves look right side up. They look different from the seedlings in the ground, which aren't wavy shaped, unless the 2 leaves are undulated, making them appear wavy.

To me, judging by the midribs, the leaves look like the left one is right side up, and the right is showing the underside...?

And yes - they look very different from the seedlings in the grass.

We haven't got enough info to id the nearby tree. Two disembodied leaves with no scale and no pictures of twigs, bark or the whole tree aren't sufficient. If we could have more pictures of the tree and also more pictures of the seedlings we might stand a chance of naming both. Also can you pull up a seedling and see if it has a seed or fruit on the bottom?

One of the leaves is definitely from the seedlings. I pulled it off and the other was loose on the ground from the tree. Also I am not sure if one is right side up and the other is upside down. It's possible. Floral- the leaves sure look like Laurus nobilis and the black seeds look like a match too.

I know Laurus nobilis. I've never had a garden without it and it self seeds on my allotment. I am certain the leaves are not Bay. If you don't believe me simply tear a leaf and sniff. That will tell you. Also Laurus nobilis produces black oval berries, not hard fruit. They looking nothing like the seeds in the photo.