Reproduction in Flowering Plants 



201 



almost endless variation in the number, form, size, color, and 

 arrangement of these parts. In some flowers the calyx or 

 the corolla may have their parts united into a tube, or one or 

 both may be wanting. Or the flowers may lack either pis- 

 tils or stamens. For example, the soft maples bear pistil- 

 late flowers on some trees and staminate flowers on others, 

 and the corn has staminate flowers in the tassel and pistil- 

 late flowers on the lower lateral branches or ears. It is not 

 our purpose to name and describe here the many different 

 variations in floral structure; a visit to a conservatory or 

 a tramp through the near-by fields and woods is a far more 

 effective way of securing an idea of the great diversity of 

 flowers. 



Pollination. If the stamens of a lily or nasturtium are 

 examined, the pollen is found to be a fine yellow powder, 

 which under a microscope will be seen to be composed of a 

 multitude of small grains. For the production of seed it is 

 necessary that the pollen grains shall be carried to the stigma. 

 This transfer is called pollination. In some plants the pollen 



FIG. 121. Flower spikes of the alder. The two clusters on the left are staminate 

 spikes ; on the right the mature pistillate spikes are shown. 



