CHAP. XXII WIND- AND INSECT-POLLINATION 97 



4. Special devices. These are particularly to help the insect 

 do the work properly. We have seen some in the 

 flowers with papilionaceous corollas, in the Larkspur, 

 Pansy, and in imperfect flowers. The number of 

 devices is manifold. Two very striking ones may be 

 studied in the laboratory if the plants are in blossom, 

 viz. : 



(a) Examine an open flower of some species of 

 Mimulus or Monkey Flower (any species, or 

 of Torenia of the greenhouses), and notice 

 the stigma. It consists of two flat pieces, an 

 upper and a lower. Selecting a stigma in 

 which the two parts are separated from one 

 another, gently stroke the inner surfaces with 

 a pin or bristle. They will soon begin to 

 move and come together. Look at them 

 from time to time and make a note of how 

 long it takes them to open. (It may require 

 an hour or more.) What is gained to the 

 flower by this device ? Write out your answer 

 in your note-books. 



() Examine a cluster of flowers of some species of 

 Barberry. Selecting an open flower, notice 

 that the stamens are lying back against the 

 petals. Gently stroke the filament of a stamen 

 and notice its movements. Do the same 

 thing to another. Make a note of this phe- 

 nomenon, and write out your opinion as to its 

 usefulness to the flower. 



(f) Kalmia or Calico-bush (called erroneously Lau- 

 rel) also shows stamen movements worthy of 

 attention. 



