40 INTERRELATIONS OF PLANTS AND ANIMALS 



well as see. Might the shape of a flower be of use to an insect ? 

 How? 



Conclusion. — 1. What do insects get from flowers? 



2. What kinds of flowers do they frequent most? 



3. What do insects give to flowers? 



Problem 14: To study cross-pollination in butter and eggs. 



NOTE. — In the fall of the year one of the best flowers for study is found in the 

 yellow butter and eggs (Linaria vulgaris) found in vacant lots and along roadsides. 

 Any cultivated forms of the toadflax family are useful for this purpose. 



Materials. — Butter and eggs or other member of the toadflax 

 family, bumblebees in formalin, needle, hand lens. (Diagrams, 

 p. 39, Civic Biology.) 



Method. — Study carefully the structure of butter and eggs 

 for any adaptations or fitness in structure : (1) to receive insect 

 visitors ; (2) to effect self- or cross-pollination. 



Observations. — Note the shape of the flower. Are all its 

 petals and sepals regular (the same size and shape) ? Might the 

 shape of the flower offer any place for an insect (as a bee) to 

 light? Try it with a bee. What would happen when the body 

 of the bee rested on the lower lip of the flower ? Press down this 

 lower lip and look inside the flower for the stamens and pistil. 

 What is there peculiar about the position of the stamens ? Hold 

 the flower in a natural position. Could pollen from the stamens 

 reach the pistil? 



Examine with hand lens the sides, back, legs, and head of a 

 bumblebee. What do you find? Now push the body of the 

 bee into an open flower. (Remember that the nectar the bee 

 seeks is held in the spur, or pointed projection, of the flower.) 

 Over what structures would the head and back of the bee rub? 

 If the bee visited another flower of the same sort, what would 

 happen ? 



Conclusion. — 1. How is the butter and eggs fitted to receive 

 insect visitors? 



2. What kind of pollination is most common in butter and eggs? 

 How is it brought about? 



3. Explain a second method of pollination in butter and eggs. 



