DICOTYLEDONS: CAMPANULALES. 7<DI 



The corolla. What represents the corolla, and how many petals are 

 indicated ? 



The stamens. What is the relation of the stamens to each other? What 

 is the name applied to such stamens? Sketch a few of the stamens to 

 show their relation to each other. 



The pistil. How many carpels are represented in the pistil ? What is 

 the indication of this? What is the relation of the different sets of the 

 flower to each other, and what is their insertion ? Give the names applied 

 to these different relations. 



The fruit. Comparing the different stages of the ripening seed, describe 

 the changes which take place in the different parts of the flower and head. 

 What parts of the flower are united in the fruit? What is such a fruit 

 called? How many seeds in the fruit? 



Seed distribution. How are seeds of the dandelion adapted for seed 

 distribution? Take a head of ripe seeds, and blow upon it. Note how 

 the seeds float; observe which end falls first upon the ground (see Chapter 

 XLV, Seed Dispersal). 



Cross-pollination. In some of the composites, as in the daisy or in the 

 sunflower, determine what provision is present for cross-pollination. Do 

 all the flowers "blossom" at the same time in a single head? Which ones 

 blossom first? Do the stamens ripen and emerge from the throat of the 

 corolla at the same time as the stigma in the same flower? Why? Com- 

 pare the dandelion in these respects. 



Material. Entire plants, with flowers (they can be obtained all through 

 the spring); heads of fruit in different stages of maturity. 



1189. The extent to which the union of the parts of the flower has been 

 carried in the composites, and the close aggregation of the flowers in a head, 

 represent the highest stage of evolution reached by the flowers of the angio- 

 sperms. The composites stand just above the bell-flowers and lobelias, 

 at the termination of a series (see paragraphs 1221, 1222). The teasels 

 show a relationship to the composites in the aggergation of the flowers 

 in a head. But the consolidation of the parts of the flower has not been 

 carried so far, and the flowers are each separated by an "epicalyx" in 

 the form of a minute cup-shaped involucre. The teasels stand at the 

 termination of another series in which are the lonicera and valerian families. 

 The gynoecium of the composites presents a highly specialized structure. 

 The ovary is plainly made up of two carpels, as shown by the two styles 

 and the internal structure, but it becomes reduced to a one-seeded achene. 

 From the five carpels in the pyrolas to the composites there is a gradual 

 tendency toward reduction in number of the carpels to two, and in the 

 composites the highest specialization is reached in the consolidation of 

 these into one achene in fruit. 



