SPONTANEOUS MOVEMENTS IN PLANTS. 291 



upon the victim, and it now requires a very considerable force to open 

 the trap. If nothing is caught, the trap presently reopens of itself, and 

 is ready for another attempt. With regard to the object of this 

 strange proceeding, there can be no doubt that the insect is retained 

 until the softer parts of the body are completely dissolved in the thick 

 mucous fluid which is exuded by the leaves ; and Prof. Asa Gray 

 considers that the evidence is nearly complete that the animal matter 

 is actually absorbed in the leaf itself. It is even stated that pieces of 

 raw beef are digested by the leaf in the same manner ! Seeing, how- 

 ever, that it is now generally admitted by physiologists that even pure, 

 water is not absorbed through the pores of leaves, which serve only 

 for the exhalation of vapor, this explanation is very hard of belief. 

 The " pitchers " of the Nepenthes, or pitcher-plant, act also as fly-traps, 

 large numbers of insects being enticed into them by the fluid they 

 secrete, and ai*e then unable to extricate themselves. 



The sensitiveness of the leaves of plants is but an excessive devel- 

 opment of the phenomenon known as the Sleep of Plants. In the case 

 of the Sensitive-plant the position assumed by the leaf and leaflets in 

 the night is the same as that which they assume when disturbed in the 

 daytime ; and with many other plants, such as the clover and the 

 Robinia or " acacia " tree, the change in the position of the leaflets, 

 morning and evening, is a familiar fact. The Sleep of Plants extends 

 also to the flowers, many plants opening their flowers only at particu- 

 lar times of the day. Thus the major convolvulus of the gardens and 

 the goat's-beard open at sunrise and always close by about noon, the 

 evening primrose opens only in the evening, and many others last for* 

 but a single day. So regular is the time of opening and closing of . 

 some flowers, that Linnreus drew up a list, which he termed a " floral 

 clock." The singular part of the affair is, that with many flowers the 

 time of opening and closing is determined, not by the degree of light, 

 or by the temperature or humidity of the atmosphere, but absolutely 

 by the hour of the day. The giant water-lily of the Amazons, the 

 Victoria rer/ia, opens, for the first time, about 6 p.m., and closes in a 

 few hours, then opens again at 6 p. m. the next day, remaining open 

 until the afternoon, when it closes and sinks below the water. Other 

 plants, again, open their flowers only in the bright sunshine, as the 

 beautiful yellow centaury (or Chlora perfoliata) the sundew {Drosera 

 rotund if olia), etc. In the latter plant, belonging to the same natural 

 order as the Venus's Fly-trap, and possessing a slight irritability of 

 the leaves, Mr. Worthington Smith has noticed also a strong sensitive- 

 ness in the petals, the flowers closing suddenly when touched. 



Irritability or sensitiveness, similar to that of the leaves of the Sen- 

 sitive-plant, is not uncommon in the flower. An instance has been 

 alluded to in the petals of the sundew ; it occurs also in the lip of the 

 corolla of several of the orchis tribe. It is, however, more common in 

 the proper organs of reproduction, as the style of Stylidium, the sta- 



