Rayless Chamomile (Matricaria discoidea) is a short plant of roadsides, unpaved driveways, and similarly disturbed habitats. The button-like flower heads are comprised of tiny yellow disc flowers, surrounded by the slightest suggestion of white ray flower petals (effectively rayless). In the top photo, notice how hundreds of flowers are open, while others have yet to bloom. This plant is also called Pineapple Weed, and indeed the leaves and flowers smell decidedly like the sweet, familiar Pineapple fruit.
The fresh or dried plant tops can be brewed as tea and used for various medicinal purposes. In his book Ancenstral Plants (2010), Arthur Haines says infusions of Rayless Chamomile can help with stress, anxiety, inflammation and various skin conditions. He also notes that, "Drinking the tea or making a stronger infusion and using it as a gargle is beneficial for oral hygiene." Read his full species account (p. 145-146) for more details.
Due to this plant's habit of growing close to roads*, I've not yet consumed Rayless Chamomile, though the fragrance of a crushed leaf or flower never fails to improve my mood. (To view the following images in full-size, click here.)