ANATOMICAL STRUCTURE AND VITALITr. 69 



towards the nearest prop or twig. In some cases they 

 are even furnished with mechanical means to obtain food, 

 for besides the curious insect traps and flowers described 

 at page 52, similar ones are provided in the leaves of 

 other plants, but in this case the entrapped insects appear 

 to be designed for the nourishment of the plant; the most 

 special instances are the Pitcher-leaf family and Venus 

 fly-traps, which see. 



Motion of Plants. — Many plants are sensible of light 

 and darkness; various flowers, such as the red pimpernel 

 and daisy shutting up in the afternoon, and the evening 

 primrose opening in the evening. Leaves also collapse / 

 and droop in the evening, as in the Clover and Pea family, / 

 being called the sleep of plants. This is not, however, 

 in all cases consequent on darkness ; motion is sufficient 

 to put to sleep the Humble and Sensitive plants, the | 

 least touch of the finger causing them to collapse and j 

 droop, thus seeming to shrink from danger, expanding 

 again when it is past. This curious phenomenon sug- 

 gests that plants have a nervous system, being of a 

 highly sensitive nature. In the Humble plant, the 

 least harsh movement or injury to a leaflet or any part 

 is sympathetically transmitted throughout its whole 

 system. Other plants with jointed leaves show their 

 sensibility, and much has been written on the subject, 

 but it is too extensive to discuss here. These move- 

 ments may be considered consequent on mechanical force 

 and darkness, difi'ering from the voluntary motion of the 

 moving plant Hcdysarum gyrans, which will be noticed 

 under its family. 



Struggle for Life. — Many plants are capable of retain- 

 ing life for a considerable period, even after being de- 

 prived of roots and leaves, which under favourable condi- 



