120 THE FLORA OF THE ALPS 



vessel an indehiscent nut. A very large order of herbs, 

 shrubs, and trees, belonging chiefly to Tropical and Sub- 

 Tropical countries, v^ith very few European representa- 

 tives ; not alpine. 



I. Urtica, Tourn. 



Flowers unisexual ; calyx 4-cleft ; stamens 4 ; leaves 

 opposite, stipulate, furnished with stinging glands. 



Our two English species of Stinging Nettle, U. dioica^ 

 L., with dicEcious ; and U7'ens, L., with monoecious flowers, 

 are equally common in Switzerland. 



2. Parietaria, Tourn. 



Flowers in dense clusters, mostly unisexual ; calyx 4- 

 cleft; stamens 4; leaves entire, without stipules; pollen 

 expelled in puffs by the bursting of the anther. 



P. officinalis, L., Wall-Pellitory, with its sub-species 

 erecta and diffusa {ramiflora, Monch.) ; common on walls 

 and rocks. 



3. HUMULUS, L. 



Flowers small, dioecious ; sepals 5 ; stamens 5 ; female 

 flowers in the axils of large membranous bracts, which 

 form a dense catkin-like spike; ovary i -celled; stem 

 twining. 



H. Ltipuliis, L., Hop. ; hedges, common. 



4. Ulmus, L. 



Flowers bisexual, in clusters; leaves with deciduous 

 stipules ; fruit a I -seeded samara. Trees with deciduous 

 leaves. 



