127a. Mature head large (>
4 cm across), shaped like a shaving brush;
involucre
concealed by whorl of prickly leaves............................. #111.
Bull Thistle.
Cirsium horridulum.
127b. Mature heads smaller (less than 4 cm across), globose;
involucre not
concealed
by leaves.................................................................
#112.
Texas Thistle.
Cirsium teanum.