84 COLLEGE BOTANY 



anth. Some flowers have neither calyx nor corolla, while others 

 have only the calyx ; but most flowers have both. 



Thestam-ens (or microsporophyllsj constitute the one or more 

 circles of organs just within the corolla. Each stamen consists 

 of a stalk-like structure known as the filament and a terminal or 

 top part known as an anther (or micros porangium) , which con- 

 tains pollen (or microspores) . The anther is composed of four, 

 occasionally only two or one, chambers known as locules. The 

 stamens may be separate or united, and are attached to the torus 

 or to the corolla. Each stamen is a specialized leaf in which 

 the petiole and mid-rib form the filament and the blade the 

 anther. Each pollen grain is a single cell. They are very 

 different in different species of plants. 



The pistil (or macrosporophyll) is the innermost one or more 

 circles of organs. Sometimes several pistils are partly or com- 

 pletely united. Each pistil is composed of a basal part known 

 as the ovary, which contains the ovules (or macros porangia) , 

 and is surmounted by a slender part known as the style, which 

 is in turn surmounted by the stigma. The stigma, is the only 

 part of the flower without an epidermal covering. The pistil is 

 subject to many modifications, but in all cases it is the central 

 organ of the flower and is composed of one or more modified 

 leaves, which may be partly or completely united. Some flowers 

 have several distinct pistils, which constitute an innermost circle. 

 Each specialized leaf of which the pistil is composed is known 

 as a carpel. If composed of only one carpel, it is simple ; but if 

 composed of two or more carpels, it is compound. 



The carpels of a compound pistil may be united in many 

 ways, but the number of carpels does not necessarily correspond 

 with the number of chambers^ Two or three or more carpels 



