The Profound Effect on the Structure of Plants 69 



in the leaves of herbaceous perennial plants, and, adapt ively 

 to this function, are greatly-swollen, soft-bodied, large-cellular 

 structures. They are leaves in the bulb scales of Lilies and Hya- 

 cinths, stems in the common Potato (the eyes being axillary 

 buds), and roots in the Sweet Potato. 



Insect Traps effect the capture and digestion of insects, and 

 thus enable some plants to augment the scanty supply of nitrog- 

 enous compounds available where they 

 grow. Adaptively thereto these traps have 

 highly special forms and accessory features 

 contributing to the attraction and capture 

 of insects, as will later be noted in a par- 

 ticular description of these plants. The 

 trap is a pitcher formed by a special cup- 

 like-upgrowth of the leaf-blade, as in the 

 various Pitcher Plants (figure 20), or else 

 a hinged or inrolling blade, as in the Venus 

 Fly-trap and Sundew. 



Flower parts contribute in various ways 

 to the efficiency of reproduction, as will 

 later appear in a discussion of that subject. 

 The parts are transformed leaves, and dis- 

 play features adaptive to their functions, 

 the green leaf-like sepals which protect 

 the other parts while in bud, the brightly- 

 colored petals which exhibit the position of 

 the flower to the visiting insect, and (though 

 with a reservation) the stamens and pistil FlG . 20. An insect-trap- 

 concerned with the actual pollination. In 



SOme kinds Of flowers the petals are miss- leaf tip in Nepenthes; one- 



third natural size. 



ing, but their function is performed by 



brilliantly-colored leaves close under the flowers, as shown so 



strikingly in the Poinsettia. 



Miscellaneous. There are, furthermore, a great many special 



