MORPHOLOGY OF HIGHER PLANTS. 



361 



together and the petiole and petiolules drooping. In other cases 

 there is a change in the position of the leaves following the alter- 

 nations of day and night. During the day the leaflets are spread 

 out freely, but at night or in darkness they droop and fold 

 together. These are spoken of as nyctinastic (nyctitropic) or 

 " sleep movements," and are exhibited by a number of leguminous 

 plants, as clover, bean, Cassia (Fig. 207), and by wood-sorrel 

 (Oxalis Acetosella) and various cultivated species of Oxalis. The 

 leaves of Oxalis as well as of some other plants fold together 



II 



FIG. 208. So-called carnivorous plants. I, the pitcher plant (Sarracenia Purpurea) 

 showing the modified pitcher-like leaves (A) with inflated portion which narrows into the 

 petiole, and a terminal, more or less spreading winged portion; and a flower and flower-bud 

 (B). II, three species of sundew: A, Drosera rotundifolia; B, D. intermedia; C, D. 

 longifolia. I, after Gray; II, after Drude. 



under the influence of intense light as well as at night or when 

 the amount of light is reduced. Of special interest also are the 

 lateral leaflets of Desmodium gyrans (telegraph plant) which 

 describe curvatures at more or less regular intervals day and 

 night when the temperature is favorable. The leaves of the sundew 

 (Drosera) are remarkable for their sensitiveness to touch. The 

 upper surface and margin are provided with peculiar hairs or 



