BIOLOGY OF THE FLOWER 



181 



bracts of the involucre are in two whorls. The small outer 

 ones become recurved when the bud opens, and the inner, 

 larger ones stand erect and protect the florets. These 

 are all alike and ligulate, and, though small, are very con- 

 spicuous when massed together in the capitulum ; the 

 corollas are yellow, but the outer, more exposed ones are 

 often brown on the back. Cut the capitulum longitudi- 

 nally and note that the florets spring from the expanded, 

 flattened end of the inflorescence- 

 axis, the outer ones being the 

 oldest. Examine a floret (Fig. 124) 

 and note that the ovary is inferior, 

 and above it is a short neck on 

 which is the calyx, represented by 

 numerous hairs which form the 

 pappus. The corolla is irregular, 

 tubular below and strap-shaped 

 above, ending in five small teeth 

 representing the corolla-lobes. The 

 five stamens are fixed to the 

 corolla, the anthers are joined into 

 a tube round the style, and the 

 pollen is shed into the tube while 

 the style is yet short. Honey is 

 secreted by a ring at the base of 

 the corolla and rises high in the 

 tube, thus being accessible to many 



kinds of insects. When the style elongates it is seen to have 

 two stigma-lobes and to be covered with hairs, which brush 

 the pollen out of the anther-cylinder. The stigmas curl 

 outwards, and their upper surfaces are covered with 

 papillae which receive pollen brought by insects from 

 another flower-head ; or self-pollination may occur by the 

 back-rolled stigmas coming into contact with pollen from 

 the same flower. 



nc- 



Fig. 124. Floret of 

 Dandelion. a, united 

 anthers ; nc, neck ; ov, 

 ovary ; p, corolla ; Pa, 

 pappus ; st, stigma. 



