Cuap. IV. VITACE.R. 143 
seems to me as striking and curious an instance of 
transition as can well be conceived. 
Cissus discolor—The young shoots show no more 
movement than can be accounted for by daily variations 
in the action of the light. The tendrils, however, 
revolve with much regularity, following the sun; and, 
in the plants observed by me, swept circles of about 
5 inches in diameter. _ Five circles were completed 
in the following times :—4 hrs. 45 m., 4 hrs. 50 m., 
4 hrs. 45 m., 4 hrs. 30 m.,and 5 hrs. The same tendril 
continues to revolve during three or four days. The 
tendrils are from 34 to 5 inches in length. They are 
formed of a long foot-stalk, bearing two short branches, 
which in old plants again bifurcate. The two branches 
are not of quite equal length; and as with the vine, 
the longer one has a scale at its base. The tendril 
stands vertically upwards; the extremity of the shoot 
being bent abruptly downwards, and this position is 
probably of service to the plant by allowing the tendril 
to revolve freely and vertically. 
Both branches of the tendril, whilst young, are 
highly sensitive. A touch with a pencil, so gentle as 
only just to move a tendril borne at the end of 
a long flexible shoot, sufficed to cause it to become 
perceptibly curved in four or five minutes. It became 
straight again in rather above one hour. A loop of 
soft thread weighing one-seventh of a grain (9:25 mg.) 
was thrice tried, and each time caused the tendril to 
become curved in 30 or 40 m. Half this weight pro- 
duced no effect. The long foot-stalk is much less 
