THE TELEGRAPH PLANT. 413 



1069. The Telegraph plant. The most surprising instance of 

 rapid spontaneous movement is that which is exhibited by the 

 lateral leaflets of Desmodium 

 gyrans. Each complete leaf 

 of Desmodium consists of a 

 large terminal leaflet and two 

 little lateral leaflets. At 

 nightfall the terminal leaflets 

 sink vertically, and the peti- 

 oles are somewhat raised, so 

 that the terminal leaflets are 

 much crowded together upon 

 the stem (see Fig. 185.) The 

 cotyledons do not have this 

 nyctitropic movement, but 

 the first true leaf sleeps just 

 as do the older ones. 



The lateral leaflets do not 

 fall at night, but at the tem- 

 perature of 36 to 38 C., or 

 even somewhat higher, keep 

 up, night and da}', an irregu- 

 lar jerking movement, which 

 has been compared to the 

 ticking of the second-hand of 

 a watch (or, formerly, to the 

 movements of the arms of a 

 Semaphore Telegraph). The tip. of the moving leaflet passes 



Papaver nudicaule and most Cichoriaceae ... 5 A. M. 



Convolvulus tricolor 5-6 " 



Convolvulus siculus 6 " 



Species of Sonchus and Hieracium 6-7 " 



Species of Lactuca 7 " 



Anagallis arvensis 8 " 



Calendula arvensis 9 " 



Arenaria rubra 9-10 " 



Mesembryanthemum nodiflorum 10-11 " 



Ornithogalum umbellatum 11 



Passiflora ccerulea 12 M. 



Pyrethrum corymbosum 2 P. M. 



Silene noctiflora 56 



(Enothera biennis 6 



Mirabilis Jalapa 6-7 ' 



Lychnis vespertina 7 



Cereus grandiflorus 7-8 ' 



FIG. 186. Desmodium gyrans. 



