POLLEN-FLOWERS 



Fig. 93. Wild Rose. Rosa humilis 

 A pollen-flower 



gathering or eating the pollen. The mulleins appear to be in 

 a transition stage. They have nearly ceased to secrete nectar, 

 and have become dependent on their supply of pollen to attract 

 insects, thus strongly suggesting that all pollen-flowers earlier 

 in their history yielded nectar. (Fig. 94.) 



19.3 



