70 Elementary Work in Botany. 



how an insect can get the nectar ? Observe the stigma. Is 

 there any adhering pollen ? If the stigma is not ready to 

 receive pollen before the pollen of its own flower has become 

 useless, it is evident that fertilization cannot take place 

 without the aid of insects heavy enough or strong enough 

 to cause the protrusion of the style. In any event there 

 would be some cross-fertilization. 



Make drawings to show this mechanism of the flower. 



EXERCISE 39. 



[Read and discuss in the class. ~\ 



Flowers and Fruits. Keep constantly in mind when 

 studying a flower the following statements and be on the 

 alert to discover evidence to prove or disprove them: The 

 work of flowers is to produce seeds. Insects usually, though 

 unwittingly, assist in this work by carrying pollen from 

 the stamens of one flower to the stigmas of another of the 

 same kind. That they may be induced to do this work the 

 flowers secrete nectar and serve it in such dishes (nectaries) 

 that only the invited guests can get it. When the feast is 

 spread the fact is signaled to the insects by the unfolding 

 of the corolla. The parts of the flower are so shaped and 

 arranged that each guest must rub against anthers when 

 they are discharging pollen, and against stigmas when they 

 are in the proper condition to receive pollen. The recept- 

 acle rarely does more than hold in place the real organs of 

 the flower. Sometimes, as in strawberries and pineapples, 

 it forms a part of the fruit. The calyx serves to protect 



