STUDIES OF SEED-PLANTS 203 



196. Petals and Sepals. The simplest flowers have only 

 the essential reproductive parts, the stamens and pistils, 

 the petals and sepals being absent. Such flowers may have 

 both stamens and pistils (i.e., are perfect) ; or some flowers 

 may have stamens (staminate), and others pistils (pistillate). 

 Willows are familiar examples of the latter. 



In many flowers, particularly of the lily family, sepals and 

 petals are present, but they are all alike in size and color. 

 In such cases where we cannot distinguish between calyx 

 and corolla, the term perianth is often used. In the most 

 common flowers the petals are larger than the sepals, and 

 usually white or colored. The sepals in some flowers are 

 small, scale-like structures, and in others they may be leaf- 

 like. Some flowers (e.g., anemone, hepatica, rue anemone, 

 marsh marigold) have no petals, but their sepals resemble 

 petals. Some flowers of this kind are at first puzzling, 

 because the leaf-like bracts (collectively called involucre) 

 on the flower-stalk may be so close to the flowers that they 

 are at first taken to be green sepals. Hepatica is such a 

 puzzle, but in the closely related anemone flower the bracts are 

 not near enough to be mistaken for sepals. In the dogwood 

 flower (really a cluster of small flowers) the bracts are large 

 and petal-like, and are commonly mistaken for petals by 

 those who have not studied botany. 



Modification of Petals. In the simplest flowers the 

 petals are free from one another; but in the highest seed- 

 plants they are more or less united into bell-shaped or tubular 

 corollas. The sepals may also be united, as in the tobacco 

 flower ; or they may be separate while the petals are united 

 so completely that only the lines of fusion indicate the number 

 of united petals (as in the morning glory). Between these 

 two extremes of fusion of petals and sepals there are numerous 

 intermediate stages which may be found in common flowers. 



197. Number of Parts of Flowers. In some flowers the 

 number of sepals, petals, and stamens is the same (often three, 



