402 GENERAL BIOLOGY 



We have learned from the studies in Chapter I to what 

 extent our common plants have become adapted to insect 

 aid in pollen transference, and how greatly they have become 

 modified in special adaptation thereto. We are now to 

 study comparatively the results in pollen production of 

 adaptations to all the various means of securing fertilization 

 including water flotation of the pollen of submerged aqua- 

 tics that bloom at the surface, and the automatic self 

 pollinating acts of flowers themselves. 



Study 52. Pollen production as affected by its mode of 

 distribution. 



Materials needed: Flowers of the nine sorts indicated 

 below : 



, f i. Tree, such as oak (fig. 235), hickory, 



< box elder or hornbeam. 

 ( 2. Herb, such as meadow rue, grass or sedge. 

 [ 3. A large open solitary flower such as 

 trillium or may -apple. 



4. An open, loosely clustered flower, such 

 Insect J as spring beauty, or buttercup, 



pollinated \ 5. A highly specialized bilateral flower, 

 such as the wood betonyor sweet pea. 



6. A composite flower, such as the dande- 

 lion (fig. 236). 

 Water pollinated. 7. A river weed (Potamogeton). 



|" 8. Open, chickweed (Stellaria media) or 

 Self J door weed (Polygonum). 



pollinated ] 9. Clistogamous, the blue violet (Viola 



l^cucullata) . 



All these will be obtainable anywhere in spring, except 

 numbers 7 and 9, both of which may be used, preserved in 

 alcohol. The clistogamous flowers of the violet may be 

 found through the whole summer after the blue flowers have 



