| All flowers are enclosed within an involucre with four marginal glands. |
| Observations should be made on the involucre as a whole, with no bracts removed. |
| Scales of the involucre dry and scarious, white or colored, imbricated in several rows. |
| The leaves of the involucre are spiny in thistles and in teazel, and hooked in burdock. |
| Fruits show 'black heel' symptom with browning of the shell and corresponding part of the involucre, which are covered with bacterial slime. |
| We used to help my grandmother gather the flowers, remove the green involucre from beneath the flowerhead and separate the rays, or florets. |
