128 



INTRODUCTION TO BOTANY 



FIG. 106. Bilater- 

 ally symmetrical 

 flower of a violet 



After H. Miiller 



flowers. A flower which has stamens only is said to be stam- 

 inate, and one which has pistils only is said to be pistillate. 



118. The perianth. In most flowers of dicotyledons the 

 calyx and the corolla are quite unlike in color and texture, 

 as they are, for instance, in roses and pinks. 

 But in many other cases, as in the (mono- 

 cotyledonous) lilies, there is no sharp distinc- 

 tion in appearance between sepals and petals. 

 This fact makes it convenient to have a single 

 name for calyx and corolla taken together, 

 and the word perianth is used to include 

 both sets of organs. 



When the calyx is composed of separate 

 sepals, and the corolla of separate petals, 

 these parts are said to be distinct, and the flower is /?//iyVj-W/ 

 or choripetalous (figs. 102 and 103). In the most specialized 

 flowers, both of mono- 

 cotyledons and of di- 

 cotyledons, the calyx, 

 the corolla, or both, 

 appear as if grown 

 together into a cup 

 or tube (figs. 101 and 

 123). This condition 

 arises from the fact 

 that the floral envel- 

 opes did not originate 

 in the form of separate 

 sepals or petals on the 

 surface of the recep- 

 tacle, but as zones of 

 tissue which developed into a tubular or cup-shaped perianth. 

 In this case the flower is said to be ^n^palau& or sympetalous,. 

 Sometimes the receptacle itself may be tubular or basin-shaped 

 and bear the perianth on its rim. Generally teeth or lobes of 

 the calyx or corolla show of how many parts it is composed. 



FIG. 107. Various types of anther 



A, iris, discharging pollen hy a longitudinal slit; 



B, barberry, discharging pollen by uplifted valves ; 



C, nightshade, D, bilberry, both discharging pol- 

 len through holes or pores at the top of the anther. 



A, B, C, after Baillon ; D, after Kerner 



