Vegetative key to the families

Either: leaves whorled; or leaves opposite and interpetiolar stipules present (Fig. 29). Herbs and woody plants
Leaves opposite; stipules interpetiolar
Leaves compound
Herbs
Style as long as stigma or shorter. Stigma elongated. Fruit with spines 3–8 mm long. Uncommon in the drier parts of the region. Probably introd. from the Mediterranean. Fl. spring–summer Caltrop T. terrestris terrestrisT. terrestris
Style longer than stigmas. Stigma hemispherical. Fruit with spines 0.5–2.5 mm long. Clay soils. Fl. spring–summer. Yellow Vine Tribulus micrococcus