EXERCISE 48 

 HOW IS POLLEN CARRIED FROM STAMEN TO STIGMA? 



Materials. A variety of wild or garden flowers growing undis- 

 turbed; hand magnifier. 



Directions for work. This is a field study. If flowers and 

 insects are not abundant at the time this exercise would natu- 

 rally be taken up, this and several following exercises may be 

 postponed, together with the corresponding parts of the text- 

 book, until a suitable time in the spring of the year. This 

 exercise might appropriately follow Exercise 105. 



Select a location where flowers of several kinds are abundant. 

 Visit the place early in the morning and observe the visits of 

 insects to the flowers. Selecting a group of flowers which appear 

 to attract insects in abundance, observe closely the actions of the 

 insects, noting how they enter a flower, how they leave it, and 

 whether they come in contact with pistil and stamens. Does any 

 pollen adhere to the body of the insect ? Is there any probability 

 that pollen is transferred from stamen to stigma in the same 

 flower ? Does the insect visit flowers of the same kind in succes- 

 sion, or does he go from one kind to another at random ? What is 

 the importance of this point ? Examine stigmas in flowers that 

 have been visited by insects and try to ascertain whether there 

 is pollen on the stigmas. It would also be of interest to inclose 

 opening buds in paper bags in order to prevent visits of insects, 

 and to note whether pollen is found on stigmas in these cases. So 

 far as you can tell, do the visits of insects result in pollinating 

 the stigmas? Does pollination appear to be accomplished with 

 pollen from the same flower (self-pollination) or with pollen from 

 other flowers (cross-pollination) ? How great is the probability 

 that cross-pollination, either with or without self-pollination, 

 occurs in practically all of the flowers visited by insects. 



Make a study of such other flowers as may be found in the 

 vicinity, noting for each such facts as are suggested below: 



1. Kinds of insects visiting each. 



2. Number of individual insects visiting a given cluster in a 

 given number of minutes. 



[60] 



