THE CALYX AND COROLLA 197 



The youngest flowers will appear simply circular in 

 outline (simple papillae of stages a and 6) : older flowers 

 will show successively 



i. The five papillae of the corolla (petals) uniting 

 at an early stage into a gamopetalous corolla-tube. 

 (Stage c.) 



ii. Five stamens, alternating with the petals. 

 (Stage d.) 



iii. Centrally, two carpels. (Stage e.) 



Other Composite may be taken as substitutes for 

 Helianthus, but some variety will be found in different 

 genera in the character of the bracteoles, and in the 

 calyx : thus in Chrysanthemum Zeucanthemum, which is 

 a useful type, the bracteoles are absent, and there is 

 no representative of the calyx. 



CALYX AND COROLLA. 



Mount in glycerine two small pieces of the corolla of 

 a ligulate floret of the Sunflower which has been kept 

 in spirit, the one with the lower, the other with the 

 upper surface uppermost. Examine under a low power 

 and note, the delicate texture and transparency of the 

 whole : the rarity or even entire absence of stomata : 

 the numerous hairs on the lower, and the small pro- 

 jecting papillae on the upper surface : and the vascular 

 bundles which do not form a dense network as in the 

 foliage leaf. 



Cut transverse sections of the same, mount in gly- 

 cerine, and observe that the structure is altogether 

 simpler than that of the foliage leaf. Note the smooth 

 lower epidermis : the upper epidermis, of which each 



