CHAPTEE XIII 

 THE FLOWER OF THE HIGHER SEED PLANTS 



147. Floral organs. The parts of a complete bisexual 

 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 



P e 





86 



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 flve circles, or whorls, 

 two 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 following one, and all the members of 

 each circle are alike (Fig. 122). 



148. Suppression and multiplication of circles. 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. 4, 10, 11, 12, 14, 15, 23). 



123 



