63 



Alighting, sucking, and pollen-collecting are thus all made 

 easy, cross-fertilization in case of insects-visiis is insured. 



FIG. 26. 

 Fig. 26. A flower of evening prim- 

 rose lUe7iothera biennis) cut lengthwise 

 shows a very long tube. (After Ker- 

 ner von Marilaun.) 



FIG. 26 A. 

 Fig. 26 A. 3, Pollen of 

 Oenothera biennis. 



and self-fertilization rendered impossible. In fine weather, 

 sufficient insect-visits are always insured by the conspicuous 



