124 THE FLOWERING PLANT. 



terminal pores, but, in the undisturbed state, is prevented from 

 falling out by the apposition of adjacent pores. Further, a 

 slender process or "tail" stretches from the base of each anther 

 towards the corolla. A bee, in trying to thrust its tongue up to 

 the nectar, is sure to touch some of these tails, the anther-ring is 

 disarranged, and a shower of pollen falls down. 



Barberry possesses irritable stamens. An insect landing on 

 the top of the syncarpous pistil (which possesses a stigmatic 

 margin) is sure to touch them in trying to get nectar, here ex- 

 creted by paired nectaries on the bases of the six petals. The 

 stamens then spring suddenly inward, not only dusting it with 

 pollen, but often frightening it off to another flower. 



We now come to some flowers in which examination of several 

 specimens will show that the same relative position is sometimes 

 occupied by the stamens, sometimes by the stigma. 



In the pink, for instance, there is well-marked proterandry, 

 and a young flower presents five stamens projecting in the centre. 

 Later on these wither, and the two stigmas are protruded in the 

 same place. In this case we have successive elongation of organs 

 which are rendered parallel by the enclosing claws of the petals. 



A similar end is served by movement of the stamens in the 

 blue meadow-geranium. Here the style rises in the centre of the 

 flower, and (as this is another case of proterandry) the five lobes 

 (stigmatic internally) which terminate it are at first closely 

 pressed together. There are five spreading petals and ten spread- 

 ing stamens. The outer five of these rise parallel to the style, 

 shed their pollen, and retire, their action being followed by the 

 five inner stamens. Now the stigmas separate, and can be polli- 

 nated. Note here that maturity is reached from without inwards, 

 as in a centripetal inflorescence. 



The rosebay willow-herb, which, by the way, presents a case of 

 proterandry known since 1790, attains the same end by move- 

 ment of the style. The whole flower is epigynous, with four 

 spreading sepals, four spreading petals, and eight stamens 

 directed downwards. The style, which resembles that of the 

 geranium just described, but possesses four lobes only, at first 

 curves back between the petals. After the pollen is shed it 

 bends forwards, and the four stigmas expand. It is hardly 

 necessary to remark that, in the four cases described, different 

 flowers are in different stages at the same time, so that the 

 expanded stigmas are sure of receiving pollen. 



Similar results to the preceding are attained, without pro- 

 terandry, in primrose and purple loosestrife, by the occur- 

 rence of bisexual flowers of different kinds (heteromorphism or 

 lieterostyly). 



