DEVELOPMENT OF THE FLOWER 113 



opposite one of the segments of the perianth to which it 

 adheres. 



3. The gynoecium, consisting of three carpels, syncarpous 

 and superior : the ovary has three loculi, ovules numerous, 

 placentation axile. 



For further details as to the various structure and form of 

 flowers, reference must be made to books on Descriptive 

 Botany. 



DEVELOPMENT OF THE FLOWER. 



In order to trace the development of the flower it is found 

 convenient to use plants with aggregated inflorescences, i.e. 

 those in which the flowers are closely associated together in 

 large numbers. By cutting sections through such an inflor- 

 escence many individual flowers, illustrating different degrees 

 of progress, will be traversed, and by comparison of these an 

 idea of the course of development may be gained even from a 

 single section. 



I. Examine young capitula of the Sunflower with the naked 

 eye : they occur in the same positions as the vegetative apical 

 buds, but differ externally from these 



1. In their greater bulk, and more especially in their diameter 

 being larger. 



2. In their colour, which is usually darker. 



3. In being covered externally by a large number of 

 imbricated bracts (or hypsophyllary leaves), which together 

 form the general involucre. 



Select a very young capitulum that is, one in which these 

 characters can be recognized, but are not as yet very pro- 

 nounced and, having removed the largest external bracts, cut 

 from it median longitudinal sections : treat with potash and 

 mount in glycerine : observe with a low power 



1. That in outline and general arrangement of parts the 

 sections resemble those of the vegetative bud, but that the 

 apical cone is broader, and more flat. 



2. That the surface of the cone has an irregular outline, 

 owing to the formation of a series of appendicular organs, which 

 are developed in acropetal order, i.e. the smallest or youngest 



I 



