Urtica L.

Tutin, T. G., Heywood, V. H., Burges, N. A., Moore, D. M., Valentine, D. H., Walters, S. M. & Webb, D. A., 1964, Flora Europaea - Volume 1. Lycopodiaceae to Platanaceae, Cambridge University Press : 67-68

1. Urtica L. 4

Annual or perennial herbs, usually with stinging hairs. Leaves opposite, usually deeply lobed or variously toothed; stipules free. Inflorescence axillary, spike-like, with clustered cymes. Flowers unisexual. Perianth 4-merous. Female flowers with more or less unequal perianth-segments, the 2 larger enclosing the achene.

1 Leaves 3- to 5-lobed; lobes serrate 4. cannabina

1 Leaves entire to serrate, but not lobed

2 Female flowers in long-pedunculate, globose heads 8. pilulifera

2 All flowers in spike-like racemes

3 Stipules2 at eachnode;upperracemesusuallymale,with the flowers usually inserted unilaterally on inflated peduncles 7. dubia

3 Stipules4 at eachnode;pedunclesof theupperracemesnot inflated

4 Plants with male and female flowers in the same raceme; petiole of lower leaves at least j as long as the lamina

4 Plants usually dioecious, or with male and female flowers in separate racemes; petiole of lower leaves not more than I as long as the lamina

6 Lower racemes female, shorter than petiole of subtending leaf; upper usually male, erecto-patent; perianth glabrous in fruit; leaves cuneate to subtruncate at the base 5. rupestris

6 All racemes similar, pendent or patent, longer than petiole; perianth hispid in fruit; leaves truncate to subcordate at base

7 Fruit with the 2 outer perianth-segments not more than | as long as the 2 inner; stem usually pubescent 2. dioica

7 Fruit with the 2 outer perianth-segments J-j as long as the 2 inner; stem glabrescent 3. kioviensis