INTRODUCTION 



13 



In some cases flowers bearing stamens or pistil 

 grow on the same plant, but separately. Thus, 

 in Maize, the upper, tassel-like flowers contain 

 only the stamens, and the lower only the style 

 and carpels or seed-vessels. 



The leaves of which the calyx is composed are 

 called sepals. These may be coalescent, separate, 

 divided, fissured, lobate, dentated, regular or 

 irregular, bilobate, tubular, pitcher-shaped, bell- 

 shaped or campanulate, etc. 



The leaves of which the corolla is composed 

 are called petals. Sometimes these are completely 

 separated (fig. 76); or they may be more or less 

 closely united, sometimes forming only a single 

 piece. 



When the corolla is united below, and more or 

 less divided above, it is said to be lobated, 

 dentated, or segmented, according to the depth 

 and character of the incisions, and the undivided 

 portion is called the cup or tube. 



Soon after the plant has flowered the corolla 

 falls off. It serves chiefly to attract insects, which 

 in many cases are necessary to fertilisation. 



The stamens likewise differ much in form and 

 structure, according to the requirements of the 

 plant. They are sometimes free, and sometimes 

 conglomerated. At the summit of the stamens 

 stand the anthers, which secrete a dust (generally 

 yellow) called pollen. 



Sometimes the stamens are fused into a single 

 tube (fig. 77); sometimes they form three clusters 

 (fig. 78) ; or, again, they may form a single cluster 

 (fig. 79). In other cases we find six stamens, four 

 of about equal length and two shorter (fig. 80) ; 

 or four, two long ones and two short ones 

 (fig. 81). 



The pistil is composed of the ovary or seed- 

 vessel, the style, and the stigma. The ovary is 

 often more or less divided into segments called 

 carpels. It is generally surmounted by the style, 

 at the end of which is the stigma. In order that 

 seed should be matured, it is necessary for the 

 pollen secreted by the anthers to be transferred 

 to the stigma. Sometimes this is effected auto- 

 matically, especially in perfect flowers; in other 

 cases the pollen is carried from one flower to 



