MEANS OF POLLINATION 



137 



nectar (for the making of honey) and may unknowingly 

 carry the pollen. Spurs and sacs are commonly nectaries, 

 but in spurless flowers the 

 nectar is usually secreted in 

 the bottom of the flower-cup. 

 Fig. 224 shows a larkspur, 

 and the envelopes are sepa- 

 rated in Fig. 225. The long 

 spur at once suggests insect 

 pollination. The spur is sepal. 

 Two hollow petals project 

 into this spur, apparently 



f 228. Staminate catkins of oak. The pistil- 

 SerVing tO gUlde the bee S late flowers are in the leaf arils, 



i_ i_ i_ i r an d not shown in this picture. 



tongue, but probably of no sig- 

 nificance. The two smaller petals, in front, are differently 

 colored and seem to serve the bee in locating the nectary. 

 The stamens ensheath the pistils. (Fig. 226.) As the insect 

 stands on the flower and thrusts his head into its center, the 

 envelopes are pushed downward and outward and the pistil 



and stamens come in contact 

 with his abdomen. Since the 

 flower is proterandrous, the 

 pollen which the pistils receive 

 from the bee's abdomen must 

 come from another flower. Note 

 a somewhat similar arrange- 

 ment in the toad-flax or butter- 

 and-eggs. (Fig. 227.) Clover 

 and alfalfa are pollinated by 

 insects. 



282. The bee is perhaps the 

 most efficient of all insects in 

 distributing pollen, for in ad- 

 dition to carrying away pollen accidentally in its search for 

 nectar, it also deliberately gathers pollen from the flowers. 



229. Catkins of a willow. A staminate 

 flower is shown at s. and a pistil- 

 late flower at p. The staminate 

 and pistillate are on different 

 plants. 



