22 
HOW PLANTS EMPLOY INSECTS TO WORK FOR 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 
y only. The thin plate or shelf is stigma only on its upper or inner face, which is 
i 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 just * 
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 different way. From its shape the blossom is called Dutch- 
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. 
