556 LECTURE XX. 



Conditions of Irritability : 



Dutrochet; M6m. pour servir, etc., I, p. 561, 1837. 



Kabsch; Bot. Zeitg., 1862. 



Darwin ; Insectivorous Plants, 1875. 



Sachs; Flora, 1863; Physiologic, 1865. 



Bert; Mdm. de la Soc. des sciences de Bordeaux, VIII, 1870. 



Darwin; Movements of Plants, 1880, p. 336. 



Bert; Me'm. de 1'Acad. des sci. de Bordeaux, IV, 1866, p. 38. 



Pfeffer; Physiol. Untersuchungen, 1873, p. 64. 



Heckel; Comptes rendus, LXXVJI, 1873; LXXVIII, 1874, p. 986 ; 



LXXIX, 1874, pp. 702, 922. 

 Darwin; Insectivorous Plants, 1875, p. 34' 

 Sanderson; The Electromotive Properties of the leaf of Dionaea, 



Phil. Trans., 1882. 

 Kabsch; Bot. Zeitg., 1861. 



Heliotropism and Geotropism: 



Darwin; Movements of Plants, 1880. 



Pfeffer; Die periodischen Bewegungen der Blattorgane, 1875, P- J 38. 



