282 PLANT FAMILIES: DICOTYLEDONS. 



The inflorescence. — What is the kind of inflorescence? Note the leafless 

 stem (flowering scape) which bears the head of flowers. Cut across the 

 stem and split it, and then describe its character. 



The involucre. — How many whorls of bracts are there in the involucre ? 

 Comparing plants in flower and at different stages of maturity, describe the 

 different positions of the involucre. 



The flowers. — Are all the flowers strap-shaped ? Note the ligula. Why 

 is it a true ligula ? Describe and sketch a single flower. 



The calyx. — What represents the calyx ? Describe the free portion, or 

 limb. Wnat is the insertion of the calyx ? 



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

 dicated ? 



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 dis- 

 tribution ? 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 on 

 seed distribution in Ecology). 



CroBS-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. 



