PROBLEM 16 



43 



the five stamens are. Make a note of their position with relation 

 to the pistil. Would self-pollination be possible in this flower? 



If it is possible to study jewel weed out of doors in its native 

 habitat, it will be found that humming birds are the visitors 

 which seem best adapted to cross-pollinate the flower. A care- 

 ful series of observations by some girl or boy upon the cross- 

 pollination of this flower might add much to our knowledge 

 regarding it. 



Jewelweed has the habit of producing (usually in the fall) 

 inconspicuous flowers which never open but which produce seeds 

 capable of germination and growth. Such flowers are said to be 

 cleistogamous. In England, where the plant has been introduced, 

 it is found to produce more cleistogamous flowers than showy ones, 

 and the showy ones do not produce seed. There are no humming 

 birds in England, and without this means of pollination, the 

 cleistogamous form prevails. 



Make a front-view drawing of the flower of jewelweed twice 

 natural size. 



Problem 16: To find other pollinating agents besides insects. 



Materials and Method. — Study as many other flowers as 

 possible, using Kny or other charts and books of reference to help 

 in your work. Suggested for this are various types of orchids 

 (described and pictured by Charles Darwin), turtlehead. Salvia, 

 and others previously mentioned. 



Observations. — Look for any peculiarities of structure that 

 seem to be for purposes of pollination. Explain. If possible, 

 study especially the structure of the flowers of sage, pea or bean, 

 and butterfly weed. 



Find out how pol- 

 lination is accom- 

 plished in the corn 

 plant ; in the pines 

 and grasses. Read- 

 ing as well as field 

 work will help here. 

 Are stamens and pis- 



