70 



INTRODUCTION 



and movable by the wind; still more rarely the flowers, or floral parts, are quite 

 immobile, or the anthers are explosive (of. 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 



Fig. 9. Arrhenatheyum elalius, M. et K., a wind-pollinated plant, (i) 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, (i) and (2), x 12 ; (3) and (4), X5. (After 

 Kerner.) 



glutinosa and incana), elm (Ulmus campestris, montana, and eff'usa), 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- 



