PARTS OF THE FLOWER 111 



4. Gyncecium of five carpels, syncarpous, superior : placenta- 

 tion, free-central, ovules numerous. 



This is an example of cohesion of sepals, petals, and 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 im- 

 bricated 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 dis- 

 tinguished 



a. Lieuiate or ray-florets, with broadly strap-shaped yellow 

 corolla, which are disposed at the periphery. 



b. 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 of which the 

 floret is produced. 



Remove the bracts from the periphery of the capitulum, 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 representing the calyx : above it is the yellow 

 corolla, tubular in its lower part, broadly ligulate above : on 

 slitting the tubular portion there may be seen a more or less 

 reduced style inserted on the apex of the ovary : the stamens 

 are abortive. These florets are thus neuter. 



Examine one of the florets of the disk in detail, noting first 

 its position in the axil of a bracteole : observe 



i. At the base the laterally compressed ovary, which is 

 inferior. 



