CROSS-FEKTILIZATION, CONCLUDED 



239 



XLV. CROSS-FERTILIZATION, CONCLUDED 



277. If the flower is to be pollinated by the 

 visit of insects, there must be some special con- 

 trivances or adaptations in the flower by which that 

 end is accomplished. Fig, 229 shows two flowers, 



Pig. 229. 

 Dimorphic flowers. 



in longitudinal section, of the polyanthus, or prim- 

 rose, of old gardens. The relative positions and 

 lengths of the essential organs are unlike in the two. 

 When an insect comes to a, it leaves upon the 

 protruding stigma some of the pollen which was 

 caught upon its body when it backed out of the 

 flower &; but when in a, it got its head dusted 



