400 MOVEMENTS. 



by the so-called Resurrection plant of California (Selagi.nella lepi- 

 dophylla) , and by the Oriental plant known as the Rose of Jericho. 

 The latter plant, when dry and shrunken into small compass, 

 takes the shape of an irregular ball, becomes detached from the 

 ground where it has grown, and may be blown about over great 

 distances ; if it has ripe seeds, these are scattered during transit. 



1042. MoTements due to changes in structure during ripening 

 of fruits. The fruit of the common Impatiens, or Touch-me- 

 not, affords a familiar instance of the movements of this class. 

 As it approaches maturity, the valves of the capsule become 

 tense, each one, so to speak, holding the others in place ; and 

 when they are disturbed by even a slight touch they separate 

 violentlj", and bj- their spring throw the seeds to considerable 

 distances. In some cases the mechanism is more elaborate, 

 notably in the cucumber-like fruit of Momordica Elaterium. In 

 this the separation of the fruit-stalk permits a sudden shrinking 

 of the whole pericarp and a violent escape of the seeds with a 

 viscid liquid through the opening made by the separation. The 

 seeds are projected considerable distances from the fruit. 



Hildebrand ^ distinguishes between (1) dry explosive fruits 

 (such as Violet, Witch-Hazel, and Lupinus luteus), and (2) 

 fleshy explosive fruits (such as Impatiens, Momordica, and 

 Cardamine hirsuta) . 



1043. Revolving moTsments, or Circumnutation. The tips of all 

 joung growing parts of the higher plants, as well as the tips of 

 many of the lower, revolve through some orbit, either a circle or 

 some form of the elhpse, the latter sometimes being so narrow 

 that it becomes practically a straight line. During its revo- 

 lution a tip bows or nods successively to all points of the 

 compass ; whence the name nutation, or, as termed bj- Sachs, 

 revolving nutation. Darwin, who re-examined the whole subject, 

 has suggested a more general term, namely, circumnutation. 



"Circumnutation depends on one side of an organ growing 

 quickest (probably preceded by increased turgescence) , and 

 then another side, generally almost the opposite one, growing 

 quickest." ^ 



1044. Owing to the fact that there are numerous instances in 

 which the revolving movements are variously modified, that is, 

 " a movement already in progress is temporarily increased in 



1 Pringsheim's Jalirbiiclier, ix., 1873, p. 235, where the whole subject is 

 discussed in an interesting manner. 



2 Darwin : Power of Movement in Plants, 1880, p. 99. 



