| 1 | Verticillasters few, usually congested into a terminal cluster or clusters. Mouth of calyx tube oblique, the upper part projected forwards. |
| 1' | Verticillasters few to many, on distant nodes, not congested into a terminal cluster or few clusters. |
| 2 | Calyx tube tubular, 8-9 mm long (in flower); calyx teeth 10. Bracts lanceolate, as long as the calyx |
| 2' | Calyx tube turbinate, 5-7 mm long (in flower). Bracts linear, shorter than the calyx. |
| 3 | Plant usually hispidous. Leaves elliptic or narrowly lanceolate. Calyx mouth open; teeth 8, subequal, the posterior one only slightly larger than the others |
| 3' | Plant usually finely puberulous. Leaves generally linear-lanceolate. Calyx mouth often constricted, especially in fruit; teeth 7-10, very unequal, the posterior one much longer than the others |
| 4 | Calyx tube curved, the mouth oblique with the upper part projected forwards. Plants sparsely hirsute. Flowers numerous (usually over 30) in a verticillaster |
| 4' | Calyx tube straight, the mouth not oblique. Plants densely woolly or tomentose. Flowers relatively fewer (generally below 20) in a verticillaster. |
| 5 | Bracts subtending the flowers nearly as long as the calyx. Stem and branches densely brownish woolly |
| 5' | Bracts subtending the flowers minute. Stem and branches tomentose |
