REPRODUCTION BY SEED 



169 



marigold, rockrose, St. John's -wort, the sweet-scented 

 spiraea, broom, and gorse. The first entomophilous 

 flowers must all have been pollen-flowers. With the 

 arrival of honey, -an additional food was offered, and great 

 economy was effected in the production of pollen. 



2. Honey-Flowers, which secrete honey or nectar. 

 Honey is a fluid rich in sugar secreted by special glands 

 nectaries which may occur on almost any part of the 

 flower. It is usually, however, secreted by a definite 

 tissue belonging to the receptacle at the base of the 

 ovary e.g., convolvulus (Fig. 67) or the stamens 



FIG. 67. Convolvulus sepium : LONGI- 

 TUDINAL SECTION OF FLOWER. 



a, nectary ; 6, superior ovary ; c, style ; 

 d, stigmas ; e, stamens ; /, petals ; 

 g, sepals ; h, bracts. 



FIG. 68. FLOWER or Ger- 

 anium, WITH SEPALS AND 

 PETALS REMOVED TO SHOW 

 HONEY-GLANDS (a). 



b, stamens ; c, carpels. 



e.g., geranium (Fig. 68). In flowers with inferior ovaries, 

 a part of the ovary- wall usually secretes it e.g., narcissus. 

 In other flowers nectaries occur on the petals e.g., butter- 

 cup (Fig. 69) ; the swollen base of the styles e.g., Umbel- 

 liferse (Fig. 70) ; as appendages of the stamens e.g., violet ; 

 or they may be specialized organs which are modified 

 stamens or petals e.g., possibly many of the Ranuncu- 

 lacese (Figs. 71, 72). It is possible that the secretion of 

 honey was first stimulated by the irritation caused by the 

 insects biting into the soft tissues at the base of the flower 

 for nutritious juices. 



