SPECIAL EXERCISES ON TYPICAL FLOWERS 215 



Note which of the disk flowers are open and which are 

 still buds. How does the blossoming proceed, that is, from 

 circumference to center, or the reverse? Remove a disk 

 flower and a ray flower. Compare them and draw each 

 enlarged. Do you find any part that represents the pedicel ? 

 The calyx? Of how many petals is the corolla formed? 

 How may the number of petals in a ray flower be determined ? 



Examine a flower just opened and find out how many 

 stamens it has. What is peculiar about their anthers? 

 Examine a flower nearer the edge of the disk. How many 

 stigmas has it? Are the ray flowers fertile (having essen- 

 tial organs) or sterile (without essential organs)? If ster- 

 ile, of what use are they to the plant ? 



Gather a few grains of pollen on a microscope slide and 

 examine it dry with a low power. Draw a pollen grain. 

 From an old flower head remove one of the disk flowers 

 which has matured, and examine it. Find the calyx which 

 forms the teeth at the top of the ovary. Remove all the 

 flowers from the disk and find the small bracts (chaff) which 

 cover it. Can you determine how many such chaff scales 

 accompany each disk flower ? Study the naked disk, noting 

 the pits or scars where flowers and chaff were attached. 



Note. Other composite flowers are the daisy, aster, fleabane, 

 goldenrod, and black-eyed Susan. Most of these are autumn 

 flowers. 



184. THE DANDELION, CHICORY, OR HAWK- 

 WEED 



The dandelion is another plant whose flowers grow in a 

 composite head. 



Method (Laboratory}. To procure dandelion plants, the 

 student should be provided with a sharp spade with which 



