CHAPTEE XIII 

 THE FLOWER OF THE HIGHER SEED PLANTS 



147. Organs of the flower. The parts found in a complete 

 flower of the higher seed plants (angiosperms) are sepals, petals, 

 stamens, and pistils (Fig. 122). The sepals, taken together, con- 

 stitute the calyx; the petals, taken together, constitute the 



pe 



se 



FIG. 122. Face view and dissection of an angiospermous flower 

 r, receptacle; se, sepal; pe, petal; st, stamen; pi, pistil; o, ovule 



corolla. The calyx and corolla are collectively known as the 

 floral envelopes, or perianth. 



Many angiospermous flowers consist of five circles, or ivhorls, 

 fif'o of which belong to the perianth, two to the stamens, and one 

 to the pistils. The parts of each circle alternate in position with 

 those of the preceding or folio icing one, and all the members of 

 each circle are alike (Fig. 122). 



148. Suppression and multiplication of circle. Any circle, or 

 part of a circle, may be suppressed. If one set of parts of the 

 perianth is lacking it is assumed to be the corolla (Fig. 123). 1 



1 For other instances of suppression of various sets, see Bergen, Flora 

 of the Northern States (Figs. 3, 8, 9, 11, 16). 



123 



