148 MOVEMENTS OF CURVATURE 



resistance, the filament suddenly straightens like a spring and scatters the 

 pollen from the dehiscing anthers. The movement takes place spon- 

 taneously, but may be accelerated by the action of pressure or contact 

 on the perianth or stamens. If the stamens are not quite ripe the removal 

 of the external resistance is not immediately followed by the straightening 

 of the filaments. Askenasy l has shown that this sudden dehiscence is due 

 to the filaments being pressed into the grooves between the anther-lobes, 

 and clinging to these with a certain energy. 



The sudden protrusion of the sexual organs in the flowers of Saro- 

 thamnns and Genista tinctoria is due to resistance being overcome or 

 removed 2 , and the same applies to the sudden opening of the flower of 

 Stanhopea oculata 3 , which produces a perceptible sound, and to the repeated 

 rapid movements of the gynostemium of Stylidium adnatntn. 



In other cases the vital activity gradually provides for the rupture 

 of the tissues at definite points, and for the sudden release of the strains 

 produced by growth. It is in this way that spontaneously, or as the result 

 of a slight touch, the fruits of Impatiens noli-me-tangere and /. balsaminea, 

 of Cardamine hirsuta and Cyclanthera suddenly dehisce, the valves of 

 the fruit rolling up with considerable force and the seeds being shot to 

 a greater or less distance away 4 . The separation of the elongated cells 

 of Zygnema and Mougeotia is effected in a similar fashion by the splitting 

 of the common wall. The sudden splitting of the cuticle, coupled with 

 the outward bulging of the end walls previously flattened by mutual 

 pressure, causes the cells to shoot apart, and the spores of Basidiomycetes 

 appear to be thrown off by the basidia in this way. Any agencies such as 

 induction-shocks, chloroform, or iodine, which aid in the rupture of the 

 cuticle, induce the sudden separation of the cells if applied when the 

 segmentation is completed 5 . 



In the case of Momordica (Ecballinm} elatcrium the fruit-stalk forms 

 a plug at the base of the fruit, and becomes loosened when the latter is 

 ripe, so that the seeds together with a slimy liquid spurt out from the 

 interior. Dutrochet 6 recognized that the required energy was derived 

 from the elastic distension of the walls of the fruit by the compressed 



1 Askenasy, Verhandl. d. naturhist.-med. Vereins zu Heidelberg, 1879, N. F., Bd. n, p. 274. 



2 Cf. Ludwig, Biologic der Pflanzen, 1895, p. 472. 



3 Pfitzer, Beobachtungen iiber Ban und Entwickelung d. Orchideen, 1877, p. 12. Reprint from 

 Verhandl. d. natur.-med. Vereins zu Heidelberg, Bd. 11. 



4 Dutrochet, Memoires d. vegetaux et d. animaux, Brnxelles, 1837, P- 22 9' Hildebrand, 

 Jahrb. f. \viss. Bot., 1873-4, Bd - Ix > P- 2 3 8 : Eichholz, ibid., 1886, Bd. xvn, p. 543; Ludwig, 1. c., 

 p. 332. Other mechanisms, including that by which the seeds of Oxalis are dispersed, are 

 discussed in these works. On the mechanism of Sphaerobolus stellatus see Zopf, 1. c., pp. 84, 374. 



5 See Benecke, Jahrb. f. wiss. Bot., 1898, Bd. xxxil, p. 453. On the fragmentation of the 

 frond of R hodomela see Tobler, Ber. d. bot. Ges., 1902, p. 361. 



6 Dutrochet, 1. c., p. 229 ; Hildebrand, 1. c., p. 238 ; Roze, Journal de Botanique, 1894, T. VIII, 

 P- 308. 





