122 PRACTICAL BOTANY. 



REPRODUCTIVE ORGANS. 



DEVELOPMENT OF THE FLOWER. 



I. Examine young Capitula of the Sunflower with 

 the naked eye : they occur in the same positions as the 

 vegetative apical bud, but differ externally from these 



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

 diameter being larger than in these. 



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 recognised, but are not as yet 

 very pronounced, and, having removed the largest 

 external bracts, cut from it median longitudinal 

 sections : treat with potash for about ten minutes, 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 appen- 

 dicular organs, which are developed in acropetal 

 order, i.e. the smallest or youngest are nearest the 

 apex, while on passing towards the periphery the size 

 regularly increases. 



Put on a higher power, and study these organs in 

 detail. 



