INSTANCES OF PHOTONASTIC AND DIURNAL MOVEMENTS 103 



possess seismonic (Mimosa) or contact-irritability (Dalbcrgia), in most cases 

 the pulvini being of value for the performance of sleep-movements. 



The nyctinastic variation movements continue usually until the death 

 of the leaf, though often their amplitude decreases, whereas the nyctinastic 

 nutation movements are performed only by the aid of those regions of the 

 petiole and lamina which remain capable of growth. Hence these latter 

 movements are shown for a few days only or for a longer period, and 

 cease when the leaf becomes adult. Usually the daily movements of 

 growing dorsiventral organs are but trifling, but the growing leaves 

 of Impatiens noli-me-tangcre, Impatiens parviflora, Sigesbeckia orientalis 

 (Pfeffer), Myriophyllum proserpinacoides (Stahl), and of Stellaria media 

 (Batalin) raise themselves upwards every evening, whereas those of Nico- 

 tiana rustica, Chenopodium albiim, and of Amaranthtis curve distinctly 

 downwards 1 . 



The flowers of various Oxalidaceae, Mesembryanthemaceae, Nymphaea- 

 ceae, and Compositae 2 perform photonastic sleep-movements. Among 

 the last-named the evening closure of the capitulum is due to the inward 

 curvature of the whole of the ligulate florets of Leontodon or Hieracium 

 (Fig. 30), but only by that of the ray-florets in Bellis. In the capitulum of 

 Chrysanthemum the spreading ray-florets bend back along the stalk at 

 night, while flowers pollinated by moths open in the evening and close when 

 morning dawns 3 . 



The leafy shoots of Mimulus Tilingii, which are obliquely or horizon- 

 tally expanded during the daytime, rise upwards in the evening 4 by the aid 

 of a photonastic reaction. It is possible also that the change in the 

 illumination aids in producing the evening sinking of the inflorescences of 

 Danctts, Falcaria, and Scabiosa, and of the flowers of Viola, although these 

 movements are mainly produced in response to the change of temperature 6 . 

 According to Morren 6 , the stamens of Sparmannia africatia perform sleep- 



1 For additional facts see the works of Hansgirg, Darwin, Pfeffer, Stahl, Jost, which have 

 already been quoted. See also Batalin, Flora, 1873, p. 437. 



2 For additional instances see Hansgirg, Pfeffer, Jost, 1. c. Also Pfeffer, Physiol. Unters., 1873, 

 pp. 195, 210; Royer, Ann. d. sci. nat., 1868, v e ser., T. IX, p. 355 ; Kerner, Pflanzenleben, Bd. II, 

 p. 208 (Natural History of Plants, 1895, Vol. II, p. 215) ; Burgerstein, Ueber die nyctitrop. Beweg. 

 d. Perianthien, 1887; Oesterreich. Bot. Zeitschrift, 1901, Nr. 6; Oltmanns, Bot. Ztg., 1895, p. 31; 

 R. Scott, Annals of Botany, 1903, Vol. XVII, p. 761 {Sparmannia}. 



3 Cf. Hansgirg, 1. c., 1893, p. 12 ; Oltmanns, 1. c., 1895, p. 50. 



4 Vbchting, Ber. d. bot. Ges., 1898, p. 39. 



'" For the literature see Hansgirg, 1. c., 1893, p. 88 ; Vochting, 1. c., 1898, p. 42, and Jahrb. f. 

 wiss. Bot., 1890, Bd. xxi, p. 285 ; Pfeffer, Period. Beweg., 1875, p. 162 ; Wittrock, Bot. Centralbl., 

 1883, Bd. xvi, p. 220 ; Kerner, Pflanzenleben, Bd. I, p. 494; Bd. II, p. 120 ; (Natural History of 

 Plants, Vol. I, p. 530; Vol. n, p. 118). According to Knoch (Bibl. Bot., 1899, Heft 47, p. 17) the 

 flower-buds of Victoria regia and Nymphaea blanda are submerged in the evening by the curvature 

 of the flower-stalk. [The fact that movements of this kind may still be performed in a hothouse at 

 nearly constant temperature points to their being photonastic in character, but direct experiment is 

 necessary to make this certain. The repeated evening closure and partial or complete submersal of 

 the flowers of the Water-lily was known to Linnaeus.] ' Cf. Pfeffer, 1. c., p. 162. 



