CHAPTER II 



MOVEMENTS OF CURVATURE 



PART I 



AUTONOMIC MOVEMENTS 

 SECTION 4. Occurrence and Distribution. 



SPONTANEOUS, autogenic, or autonomic movements would arise in the 

 normal course of development even if the external conditions could be kept 

 rigidly constant. Locomotory and streaming movements will, however, be 

 discussed in a subsequent chapter. Movements may either be periodical, 

 as when a shoot nutates or a leaf folds at night, or may be incapable of 

 repetition (ephemeral or climacteric), as when a bud unfolds or a capsule 

 dehisces 1 . Periodic or nutation movements are shown by the growing apices 

 of both vascular and non-vascular plants, and in the latter by the growing 

 tips of single cells such as the branching mycelium of Mucor, and by fila- 

 ments formed by chains of cells such as those of Penicillium or Spirogyra 2 . 

 This was first shown by Darwin 3 , and Fritsch has repeated some of the 

 observations under conditions kept as constant as possible, and has found 

 that the autonomic movements still continue. 



When the movements are pronounced, their independence of the 

 external conditions is easily seen. Thus the growing ends of the stems of 

 climbers sweep round in wide circles, as also do many tendrils ; while the 

 lateral movements of the peduncle of Ttdipa and Allium may cause the 

 flower to be bent downwards during development 4 . Individual cells or 



1 A. P. de Candolle (Memoires d. savants etrangers de 1'Institut de France, 1806, T. I, p. 338) 

 termed flowers opening once ephemeral, and those opening repeatedly equinoctial. 



2 F.Darwin, Bot. Ztg., 1881, p. 474; Fritzsche, Ueber die Beeinflussung d. Circumnutation 

 durch verschiedene Factoren, Leipziger Dissertation, 1899, p. 9 (Phycomyces) ; Wortmann, Bot. Ztg., 

 1 88 1, p. 384 (Mucor stolonifer). 



3 Darwin, The Power of Movement in Plants, 1880. Darwin and, later, Fritzsche have shown 

 that a slight change in the external conditions may influence the movements. On Fungi cf. Rein- 

 hardt, Jahrb. f. wiss. Bot., 1892, Bd. xxin, p. 479 ; Sokolowa, Das Wachsthum d. Wurzelhaare und 

 Rhizoiden, 1897. In most of Darwin's experiments the attached indicator exercised a certain 

 disturbing action. 



* Cf. Darwin, 1. c., and the works already quoted; also Hofmeister, Pflanzenzelle, 1867, P- 3 2 3 J 

 Lecoq, Bull, de la Soc. bot. de France, 1867, p. 153 (Leaf of Colocasid) ; F. Miiller, Jenaische Zeitschr. 

 f. Med. u. Naturw., 1870, Bd. v, p. 134 (Peduncle of Alisma)\ Sachs, Lehrbuch, 3. Aufl., 1873, 

 p. 827; Rodier, Compt. rend., 1877, T - LXXXiv, p. 961 (Ccratophyllum}\ Wiesner, Bewegungs- 

 vermogen, 1881 ; Vochting, Bewegungen d. Bliithen u. Friichte, 1882, p. 186, &c. ; Hansgirg, 

 Phytodynamische Unters., 1889; Beihefte Bot. Centralbl., 1902, Bd. xil, p. 248; Phycol. und 

 phytophysiol. Unters., 1893; Askenasy, Eer. d. bot. Ges., 1890, p. 77 (Root of Maize); A. Schulz, 



C 2, 



