70 INTRODUCTION 
and movable by the wind; still more rarely the flowers, or floral parts, are quite 
immobile, or the anthers are explosive (cf. Delpino’s groups, p. 62). 
Wind-flowers are also dichogamous or diclinous, so that self-pollination is 
entirely or partly prevented. ' 
A great many of our trees and shrubs, indigenous or introduced, that flower 
in spring, are pollinated by the wind, e.g. hazel (Corylus Avellana), alder (Alnus 
Fic. 9. Avrrhenatherum elatius, M. et K., a wind-pollinated plant. (1) A closed anther. 
(2) A dehisced anther. (3) Spikelet with widely opened glumes, and anthers hanging down in still 
air. (4) Spikelet exposed to wind. The pendent anthers of one flower are discharging pollen; the 
anthers of another flower are empty; one anther has dropped from its filament; the anthers of a third 
flower that is still closed are just beginning to protrude. (1) and (2), x12; (3) and (4), x5. (After 
Kerner.) 
glutinosa and incana), elm (Ulmus campestris, montana, and effusa), plane (Platanus 
orientalis and occidentalis), walnut (Juglans regia), beech (Fagus sylvatica), oak 
(Quercus pedunculata, sessiliflora), hornbeam (Carpinus Betulus), birch (Betula 
verrucosa, pubescens, humilis, nana), poplar (Populus alba, tremula, nigra, molinifera, 
balsamifera), ash (Fraxinus excelsior), and others. Well-marked cases of wind-pollina- 
