iv.] FURZE, 93 



and the stamens and pistil are again protected ; in 

 Genista tinctoria, on the contrary, the flower opens 

 once for all. The keel is at first nearly parallel to 

 the standard (Fig. 74). This position is, however, 

 one of tension ; the keel is retained in it by the union 

 of its upper margins, which inclose and retain the 

 curved pistil which presses against them like a spring. 

 The sides of the keel have near the base a projecting 

 lobe (Fig. 76 m), which locks with one at the corre- 

 sponding part of the wing. When an insect, alighting 

 on the flower presses open the keel in search of pollen, 

 as soon as the curved end of the pistil is set free, it 



FIG. 74. Flower of Genista tinctorta unopened. 



FIGS. 75, 76. Ditto, opened, std, standard ; iv, wing ; k, keel ; m, projection on keel. 



springs up with a jerk, the keel, on the contrary, 

 springs back (Figs. 75 and 76), and the pollen is ejected 

 in a shower. It appears that the flowers do not open 

 of themselves if insects are prevented from visit- 

 ing them (Henslow, your. Linn. Soc. t v. x. p. 468). 



Genista tinctoria contains no honey, and yet it is 

 visited by several insects which do not consume pollen. 



The flowers of the Common Furze (Ulex Europceus] 

 agree in essentials with those of the preceding species. 

 The calyx, however, is larger, and coloured ; the 

 wings are longei in proportion and project beyond the 



