PARTS OF THE FLOWER 191 



carpels, and of adhesion of the stamens to the corolla. 

 Note also that the flowers are of two types, short-styled 

 and long-styled (dimorphic). 



VI. Examine a head or capitulum of the Sunflower : 

 this is an inflorescence, and it is composed of a large 

 number of florets, or small flowers, inserted on a wide, 

 disk-like development of the main axis or peduncle. 

 Note the dark green, closely imbricated bracts, which 

 show a gradual transition from the foliage-leaves to a 

 simpler form : these together constitute the involucre, 

 which surrounds the margin of the capitulum. On 

 the upper surface of the flattened receptacle are the 

 numerous, and closely packed florets, of which two 

 types are to be distinguished 



a. Ligulate or ray-florets, with broadly strap- 

 shaped yellow corolla, which are disposed at the 

 periphery. 



&. Tubular or disk-florets, which constitute the 

 central part of the head. 



In the young inflorescence before flowering, and also 

 later in the fruiting inflorescence, there may be seen 

 opposite, and external to each floret a small leaf (the 

 bracteole), lanceolate above, but broadly sheathing 

 below, in the axil tof which the floret is produced 

 (compare development, p. 194). 



Remove the bracts from the periphery of the capit- 

 ulum, and separate a single ligulate floret : examine 

 it in detail, and observe at the base the more or less 

 compressed ovary, which is inferior : at its upper limit 

 is an irregular rim, which may be regarded as repre- 

 senting the calyx : above it is the yellow corolla, 

 tubular in its lower part, broadly ligulate above : on 



