VEGETATIVE REPRODUCTION. I97 



The parts and functions of the flower of seed plants are 

 now to be discussed. 



The Flower. 



278. A flower usually consists of a shortened axis, the 

 torus, bearing several floral leaves (figs. 66, 152). The 

 spore leaves are known as 

 essential organs, the accessory 

 leaves as the perianth and 

 bracts. 



The essential organs are of 

 two sorts, stamens and carpels. 

 In any flower they may be all 

 stamens or all carpels, or may 

 include both sorts. The 



, - 1 r FrG. 152. — A flower of linden, halved; show- 



perianth may be composed of mg a pestle-like pistil. Magnified about 

 , . , f. ^ 3 diam. — After Kerner. 



one or two kinds of leaves, 



often bright-colored. If there are two sorts, those next the 

 spore leaves are generally highly colored, and constitute the 

 corolla. Each leaf of the corolla, when distinct, is a petal. 

 The leaves below the corolla are often green. They con- 

 stitute the calyx, and each, when distinct, is a sepal. 



279. Carpels. — The leaves bearing the ovules ^re called 

 carpels. They may be flattened; or so curved that in the 

 course of their development the edges unite and a cavity is 

 more or less perfectly enclosed; or neighboring carpels may 

 grow together in such a way as to form a case. Such hollow 

 structures, whether composed of one or more carpels, are 

 often somewhat pestle-shaped, whence they early received 

 the name pistil (fig. 152). A flower whose only essential 

 organs are pistils is ciW&A. pistillate. 



280. Ovules. — ^Among seed plants the spore cases which 

 the carpels bear are universally known as ovules, a name 

 given to them under the supposition that they were the eggs 

 which, upon fertilization, produce new plants. Though they 



