40 



BOTANY 



or less thickly covered with hairs, and the wings are thatched with 

 hairlike, tiny scales. All these structures are of use to the 

 flower because they collect and carry pollen. On each side of the 

 head of a butterfly is a long, fluffy structure, the palp. This 

 collects and carries a large amount of pollen, which is deposited 

 upon the stigmas of other flowers when the butterfly pushes its 

 head down into the flower tube after nectar. 



Flies and some other insects are agents in cross-pollination, as 

 we shall see during some of our later studies. Humming birds 



are also active agents 

 in some flowers. Snails 

 are said in rare in- 

 stances to carr}^ pollen. 

 Man and the domesti- 

 cated animals un- 

 doubtedly frequently 

 pollinate flowers by 

 brushing past them 

 through the fields. 



Field Flowers. — Let us 

 now take up some com- 

 mon wild flowers easily 

 found in the fall of the 

 year, and work out the re- 

 lation of the parts of the 

 flower to its insect visit- 

 ors. Remember that the 

 important part of these 

 exercises is to find how 

 and by what means the 

 flower is adapted or fitted to receive the visits of insects. This work can 

 be done best on field trips, but it can readily be modified so as to be useful 

 as a schoolroom exercise. 



The Evening Primrose (Onagra biennis) . — The habitat preferred by 

 this flower is dry fields, roadsides, or waste places. The yellow flowers are 

 found in long, upright, densely crowded clusters. A flower cluster in which 

 the individual flowers have no flower stalks or pedicles, with one main axis 

 to the cluster,, is called a spike. Notice that young and old flowers and 

 fruits are all on the same cluster. Where are the youngest flowers located 

 in the cluster? Is there any flower at the end of the main stalk? Could 

 you determine in advance the length of the flower cluster ? Such a cluster 

 is said to be indeterminate. Why? Study a single open flower. Note 

 the caljrx and corolla; are the parts distinct? How many petals do you 

 find ? Notice that there are eight stamens and that the stigma is four-parted. 

 Cut the ovary in cross section and see how many locules there are. 



A humming bird just about to cross-pollinate a flower. 



