Humungargantuan cotton balls . . .

I've had a lot of great book visits in the last week and I hope to get pics posted soon but I had to ask a quick question about this:

I saw these gigantic cotton balls hanging from a tree outside the Coronado Library and I felt like I stepped inside a Dr. Seuss book.  You'd think being in California I would have seen these before but I haven't.  What are they?  Or maybe I DID step into Seussland?