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THE BOOK OF NATURE STUDY 



style. There are three stamens, attached to the inner surface of 

 the larger perianth segments, and standing up opposite to these. 

 Each stamen has a strong curved stalk and a large anther, the 

 two lobes of which face and open outwards and downwards. 

 Three styles spring from a cylindrical portion in the centre of 

 the flower terminating the inferior ovary. The styles are broad 

 and leafy, or petal-like, and they lie opposite to the broad outer 

 perianth segments, and thus above the three stamens. Each 



stamen is thus enclosed 

 between the perianth seg- 

 ment and the leafy lobe 

 of the style, which fit 

 closely together and hide 

 the stamen. The tip of 

 the style is two-lobed, and 

 has a wide thin margin 

 and is bent upwards. Just 

 before this bend takes 

 place a little projecting lip 

 can be seen on the under 

 or outer surface of the 

 style. This is the stigma, 

 the upper surface of the 

 lip being the receptive 

 surface. The fact that 

 the branches of the style 

 do not alternate with the 

 stamens indicates that an 



inner whorl of three stamens is wanting in this flower. As a work- 

 ing arrangement in pollination each third of the Iris flower can 

 be compared with an irregular flower. Humble-bees are mainly 

 concerned in the pollination. These alight on the broad landing- 

 place formed by one of the outer perianth segments, and, guided 

 by the brown lines or honey-guides on this, will force it and the 

 style apart. Having crept in between the perianth-leaf and the 

 style, the bee can reach the nectar by a passage to either side of 

 the stalk of the stamen, where this is attached to the perianth. 

 In thus creeping into the flower the bee first rubs its back against 



FlG. 101. Flower of Yellow Flag cut in half, y^ 

 outer segment of the perianth ; z, inner segment 

 of perianth ; s, stamen ; g t branch of the style ; 

 a, the stigmatic lip. (After Warming.) 



