FLOWERS 191 



169. POLLINATION 

 Object. To learn what is meant by self-pollination- 



Apparatus. Flowers of closed gentian, fringed milkwort, or 

 the common cleistogamous flowers of the blue violet. 



Method. Examine the flower to be studied. Cut open 

 the ovary and find the seeds. Does the plant receive pollen 

 from any other plant? If not, whence comes the pollen 

 which has made the ovules mature into seeds. If the 

 flower does not open, the pollen cannot have been borne 

 on the winds or brought by insects. From what source 

 must it have come? 



Conclusion. What is self-pollination ? 



Suggestion. (a) Look for cleistogamous flowers at the 

 root of violet plants. Notice that such flowers are lacking 

 in the color, odor, and nectar which are so abundant in the 

 ordinary flowers of the violet. 



(6) Can a plant be pollinated artificially ? Hint : Having 

 removed the stamens from a freshly opened flower, fill a 

 camePs-hair brush with pollen. Gently brush it over the 

 stigma and then inclose it in a paper bag. This will pre- 

 vent any other pollen from getting on. After ten days 

 remove the bag and note the result. 



(c) Make the same experiment, using pollen from other 

 kinds of plants. What result? Does it make any differ- 

 ence whether the pollen is fresh or old ? 



(d) Is the stigma as receptive at one time as another? 

 Examine hollyhock flowers on the same spike. How do the 

 stamens of the upper flowers differ from those of the lower 

 ones ? How do the pistils differ ? 



(e) Walk in a field or pasture where there is English 

 plantain growing, or observe any mint or mallow. Are all 



