From the Floral Design Institute's web page:

Common Names: Billy Balls, Billy Buttons
Botanical Name: Craspedia, (crass-PEE-dee-a)
Availability: May through October
Vase Life: 10 to 12 days
Storage Temperature: 36 - 38 F
Ethylene Sensitive: No
Description: Firm, one inch, globe shaped flower heads at the end of long slender stems without foliage.
Colors: Yellow
Botanical Facts:
Design Notes: These unusual blossoms add wonderful texture and visual interest to floral designs.
Purchasing Hints: Purchase full colored heads that show no signs of shedding pollen.
Conditioning: Cut under water with a sharp knife. Hydrate in a solution of warm water and commercial floral preservative / floral food for two hours before storage or usage.
Additional Notes: These flowers dry well for use in permanent arrangements.