PRAIRIE FLOWERS IN AUGUST 53 



Composites. They form the largest family of flowering 

 plants on earth. Do you think there are many of them 

 growing in this locality? For to-morrow's lesson, bring 

 me as many different kinds of composites as you can find. 

 Do all Asters, Thistles, and Dahlias belong to the com- 

 posites ? How are the seeds of Thistles and Dandelions 

 disseminated ? 



In our next lesson we shall study the cultivated Sun- 

 flower ; it is the largest of our composites and shows the 

 typical structure very clearly. 



28. The Sunflower. Helianthus annuus. 



MATERIAL : Cultivated sunflowers at different stages of develop- 

 ment ; other composites for comparison. 



The cultivated Sunflower might well be called the Giant 

 Flower. In good soil you can find some whose flower heads 

 measure from six to ten inches across. If the plant has 

 room, it is copiously branched; its stem is then about as 

 thick as a man's arm, and may attain a height of seven 

 feet. 



Each head consists of a large number of little tubes and 

 a row of strap-shaped rays on the outside. A single one 

 of these little tube-shaped flowers, if placed by itself, would 

 not be at all conspicuous, and could not easily be seen by 

 insects. The fact, however, that thousands of them are placed 

 in one head, and there surrounded by a crown of large, bright 

 rays, makes the ivhole head very conspicuous. On a warm 

 day you will find a large number of bees and other insects 

 busy drinking the honey from the thousands of little wells. 



The little tubes open in rings, beginning on the outside 

 of the head. Look at this large head. Here is a ring of 



Common ragweed, giant ragweed, false sunflower, dog fennel, Canada 

 thistle, burdock, sweet clover, Russian thistle. 



