122 THE STRUCTURE OF FLOWERS. 



irregular. The flowers are almost horizontal, closely com- 

 pacted against the axis, and consequently not readily visited 

 on any side except from the front. The style and stamens 

 curve upwards, so that " the smaller bees and flies thrust 

 the head or proboscis from the front into the flower, and the 

 upward curvature of the style and stamens causes the insect 

 to enter by the lower half of the flower, and so to get dusted 

 with pollen from above." * 



Miiller also notices, about this flower, that " the style, 

 which even in the bud overtops the stamens, grows very 

 markedly after the flower opens, as the flower itself does. 

 As a rule, it attains its full length only after the anthers 

 have completely shed their pollen, at which time also the 

 four-lobed stigma reaches its full development." 



He gives five figures of Saxifraga Seguieri to show the 

 progressive stages of development. In the first or female 

 (protogynous) condition the stigmas only are mature, the 

 anthers, petals, and sepals being far from having attained 

 their full size. It is not until half the anthei-s have shed 

 their pollen, and the others ready to do so, that the flower 

 attains its complete dimensions f 



I refer to these facts, which are equally applicable to 

 many other flowers, to show that growth normally continues 

 after insects have commenced to visit flowers ; so that there is 

 plenty of opportunity for the petals, stamens, etc., to respond 

 to the insect's action before reaching maturity. 



Dr. F. Noll has investigated the various movements of 

 zygomorphic flowers during growth, resulting in the external 

 position of the flower; and he finds that the excess of 

 weight on one side is, when necessary, counterbalanced by 

 active tensions (see Jl. B. Mic. Soc, 1887, p 612 and reffs.). 



* Fertilisation, etc., p. 379. t Ii>id, p. 244. 



