LESSONS WITH PLANTS 



333 



to recognize but understand 

 way. 



The common sunflower is 

 the structure of com- 

 posites. A few belated 

 specimens may still be 

 found in the fall when 

 school begins. But the 

 single garden zinnias, 

 and single asters, the 

 wild sunflowers, and the 

 daisies will do very well. 

 At first thought one 

 would think that what 

 is generally called a sun 

 "flower" is really a sin- 

 gle flower, but closer ex- 

 amination will reveal 

 the fact that this is an 

 aggregation of hundreds 

 of very small flowers 

 massed together in a 

 flat head. Note first the 



the structure of in a general 

 perhaps the best for teaching 



FIG. 132. Pussy-willows. 

 (The pussies are flower buds.) 



green calyx-like leafy 

 scales on the outside of 

 the whole. This is not a true calyx, but is called an in- 

 volucre. Note how the scales are in several overlapping 

 rows. Next within the green involucre comes a circle of 

 flat, ribbon or strap-shaped, colored parts that are often 

 wrongly called petals. They are not petals, but whole flow- 

 ers. Pull out some of these flowers. Note that the flat 



