A NATURALIST IN BRAZIL 



The pollinia may be made to spring off and adhere to a pencil or 

 a needle if this is thrust into the spur ; when withdrawn, the two 

 little horns will be seated upon it. As the insect flies away, the 

 pollinia, actuated by an internal mechanism, bend forwards, and 

 when the insect visits the next flower they inevitably strike the 

 stigma, to which the pollen adheres, whereby fertilization is effected. 

 In the Silkweeds or Milkweeds (Asclepiadeae) there are tiny gins 

 or "pinch-traps" which adhere, with the pollen, to the feet of the 



Fig. 14. — A Tropical Orchid. N, the entrance to the spur con- 

 taining the nectary, in which the stigma is situated. Above N 

 are the club-shaped pollinia {pp). The insect alights on the 

 stool [s), and thrusts its head into the orifice. Touching 

 the triggers {t), it releases the pollinia {pp), which spring off 

 on to its head and there adhere. As the insect flies away they 

 fall forwards, striking the stigma of the next flower visited 



visiting insect; and these gins are actually set in slots into which 

 the insect is obliged to put its feet, as the petals are smooth and 

 slippery. In other flowers the stamens are like turnpike bars ; they 

 fall down upon the entering insect when it touches a spring in the 

 vestibule of the nectary. The flowers of the Fig-cactus too have a 

 fascinating mechanism. From a pit filled with nectar rises the pistil 

 with its stigma, and the stamens stand around it in a circle. When 

 an insect arrives it settles on the stigma and tries to climb down to 

 the nectar. But in doing so it touches the stamens, and these are 

 so contrived that on being touched they curl over in groups, and 

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