

THE DEHISCENCE OF ANTHERS BY APICAL PORES. 251 



structures. The relation of flowers to insects is one of the 

 oldest phases of ecology, and while SprengeFs beautiful 

 observations of over a century ago were neglected until the 

 theories and researches of Darwin and his contemporaries 

 showed their importance, it was not long after the revival 

 of interest in this fascinating branch of natural history 

 that students began to see that if flowers show a reduced 

 degree of fertility with their own pollen and are so closely 

 adapted to some special visitor or group of visitors that . 

 others are unable to pollinate them, their geographical 

 range will depend largely upon the distribution of the ani- 

 mals which are able to effect their pollination. That this 

 phase of morphology and geography should have been 

 neglected seems all the more remarkable in view of the 

 significance assigned to floral structures in classification. 



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considers animals as factors in plant distribution. Certain 

 floral types, he considers, are undoubtedly limited in their 

 geographical distribution by the range of the animals 

 which pollinate them. The problem of adaptation for the 

 protection of the plant from animal enemies has been much 

 less satisfactorily investigated except in the case of 

 myrmecophilism. 



One of the best classes of data for the investigation of 

 this problem is that furnished by ornithophilous flowers, 

 since birds which are of importance as pollinators are of 

 restricted range, and the adaptations, when they are real 

 and not merely apparent, are evidently dependent in their 

 range upon that of the organisms to which they are adapted. 

 Comparatively few plants are ornithophilous, but the evi- 

 dence offered is of such a character as to give us confi- 

 dence in attacking the more difficult problem offered by 

 entomophilous forms. Entomophily is the more general 

 condition and in its geographical range is practically coex- 

 tensive with the limits of the Phanerogams. Only three 

 orders of insects seem to have influenced essentially the 



