General: Perennial herb from a stout creeping rhizome; stems erect, simple below but freely branching above, glabrous, with milky juice, 15-30 cm tall.
Leaves: Stem leaves alternate, lower leaves linear, 1-3 cm long, 1-3 mm wide, glabrous, leaves of axillary upper branches more numerous and narrower.
Flowers: Inflorescence of many-rayed umbrella-shaped clusters; floral bracts oval to heart-shaped; involucres 3 mm long, bell-shaped; glands reddish-green, horned.
Fruits: Capsules, finely warty; seeds 2 mm long, pale yellow, glabrous.
If more than one illustration is
available for a species (e.g., separate illustrations were provided for two
subspecies) then links to the separate images will be provided below.
Note that individual subspecies or varietal illustrations are not always available.
