122 



drilling' to yet at the nectar as food, or as a substitnte for water in temper- 

 ing tlieir building material. Hnnible and lionej'-bees occasionally were 

 seen prospecting around the flowers, but they rarely stopped for more 

 than a moment. 



It is remarkable, while the mechanism of Tecoma is peculiarly effective 

 in preventing self-pollenation, that its j)ollen is impotent except when 

 applied to the stigma of another plant under restricted conditions, and 

 that the humming-bird is us only visitor of service in its fertilization. 



Impaticns aiirea Muhl. The pale toi:ch-me-not is a common plant in 

 Indiana, growing best in the damp, rich soil of the shaded river bottoms. 



The mechanism of the flower is generally understood, but the part 

 played by the scales, on the inner side of the filaments, is not so well 

 known. The filaments are so arranged as to form a group, which is held 

 together by the coherent scales. With reference to the moutli of the spur 

 the posterior part of the group is closed by a single filament and the sides 

 by tAvo filaments, leaving the front with a larger opening between the 

 anterior pair than elseAvhere. The scale of the posterior filament is di- 

 vided into two parts which are continuous with the coherent scales of the 

 sides. The two resulting appendages are symmetrical, and are in close 

 contact, on an antero-posterior line, so as to form a roof or hood over the 

 end of the stigma. On the under side of the hood is a pocket into which 

 the stigmatic end of the ovary is inserted. The end of the ovary is 

 marked by a slight papilla near the anterior end of the dividing line of 

 the hood. The pocket is so placed with reference to the plane of the hood 

 that the end of the ovary does not push at right angles, but in an oblique 

 direction. The filaments cease to grow when the flower opens, while the 

 ovary continues to increase in length, and by this arrangement with refer- 

 ence to the hood it pushes against it without protruding, until the fila- 

 ments are broken from their attachment to the receptacle. When the con- 

 nection with the receptacle is broken the filaments curl backward with 

 such force as to often cause the cap of withered anthers to fall to the 

 ground. If this does not happen, the cap is easily displaced by the first 

 insect-visitor that attempts to enter the spur. 



When it is recalled that the touch-me-not floAver is suspended from the 

 end of a slender peduncle, and bobs and swings with every breeze or 

 touch of an insect, the function of the hood in excluding self-pollenation 

 becomes evident. Observations show that the hood is frequently covered 

 with pollen that has sifted througli the chink between the anthers, or has 



