Involucre

The FNA describes the H. pumilus (little sunflower) involucre as cylindric. It could pass for hemispheric too.

The phyllaries of this involucre are lanceolate, bordering on ovate. The apices are acuminate, meaning they they taper to a point with concave sides.

The involucre is imbricate and the phyllaries are in a 3-series. The phyllaries are equal (roughly the same size) and loosely appressed (flat against one another, but in a relaxed way).

To round out the description, the phyllaries are covered with stiff, white hairs. In botanical terms, they're hispid (covered with stiff hairs) or strigose (covered with stiff, appressed hairs) depending on the flower and the describer. In this example, most of the hairs are appressed with just a few sticking out. Scabrous, meaning rough to the touch, is another term sometimes used to describe them.