22 



HOW PLANTS EMPLOY IN8ECTS TO WORK FOK THEM. 



difficulty. The anther and the stigma face away from each other. The anther 

 faces outwards and discharges its pollen through two long slits on the outer side 

 only. The thin plate or shelf is stigma only on its upper or inner face, which is 

 roughened and moistened in the usual way for receiving the pollen : the face 



turned towards the anther cannot receive the 

 pollen at all. 



40. A less common flower, the beautiful 

 Arethusa, of our northern bogs (Figs. 13, 

 14), is quite as curiously arranged so as jiiM 

 not to do of itself what is obviously intended 

 to be done. The stamen and the style are 

 united into a long and wing-margined col- 

 umn ; the stigma is a shelf; and the anther, 

 which is shaped like a helmet, and is fixed to 

 the top of the column by a hinge at the back, 

 rests upon this shelf, its front edge at bottom 

 projecting slightly over its edge, — just as 

 the lid of a chest projects a little over the 

 front side, for more convenient lifting. The 

 anther holds four soft and loose pellets of 

 pollen, which are ready to fall out when the 

 anther is uplifted. But here again, only the under side of the shelf is actually 

 stigma ; the pollen lies imprisoned on the upper surface, and can never of itself 

 reach the lower surface, where alone it can act. 



41. There are hundreds of such cases, differing more or less in the arrange- 

 ment, but agreeing in this, that the pollen is placed tantalizingly near the stigma, 

 yet where it can never reach it of itself, or can seldom and only accidentally do 

 so. Surely, if we had the making of these blossoms, we should have turned the 

 shelf under the anther of Arethusa the other side up, and have restored the har- 

 mony of that averted couple in Iris by turning the two face to face in place of 

 back to back. 



42. The flower of Aristolochia Sipho, or Pipe-vine of the Southern States (a 

 large-leaved woody twiner which is cultivated for arbors), shows the same extra- 

 ordinary aversion in a difierent way. From its shape the blossom is called Dutcb- 

 man's-pipe : it is a tube curved round on itself, largest at the base, contracted at 



Fig. 12. Iris-flower cut lengthwise, showing 

 one stamen and stigma. 



