328 



LOCOMOTORY AND PROTOPLASMIC MOVEMENTS 



however, where the chloroplastids are numerous and usually lens-shaped they 

 move in the protoplasm lining the cell to the face or profile positions. It is 

 in this way that the chloroplastids in a filament of Vaucheria collect in two 



parallel rows along its upper 

 and under-surface when feebly 

 illuminated from beneath, but 

 along its sides when the light 

 is intense and a profile posi- 

 tion is assumed. Similar re- 

 actions are shown in the leaves 

 of Mosses and of Elodea> as 

 well as in the fronds of Lemna 

 and in Fern-prothallia *. 

 Under moderate vertical illu- 

 mination the chlorophyll 

 bodies assume the face posi- 

 tion by placing themselves 

 upon the outer and inner 

 walls, whereas in intense light 

 they group themselves upon 

 the side walls (Fig. 54 B). 

 Owing to the special internal 

 relationships the chloroplas- 

 tids do not spread themselves 

 uniformly in darkness, but 

 place themselves upon the 

 inner and side walls (Fig. 



540- 



In very intense light 



irregular aggregations and 



groupings of the chloroplastids are often shown, not only in the simple 

 tissues mentioned, but also in the more complex ones of higher plants 2 . 

 Aggregation is rapidly produced in the chloroplastids of Acetabularia 

 mediterranea 3 , whereas in Vaucheria long exposure is necessary and in 

 Nitella no aggregation at all is shown 4 . We are here dealing with internal 



Oltmanns, Flora, 1892, p. 207 ; Lewis, Annals of Botany, 1898, Vol. xn, p. 418. Wittrock observed 

 (Stahl, 1. c.) that the chlorophyll plates of Gonotonema reacted similarly. 



1 Frank, Jahrb. f. wiss. Bot., 1872, Bd. vin, p. 216; Schimper, Jahrb. f. wiss. Bot., 1885, Bd. 

 xvi, p. 203 ; Stahl, 1. c. ; Haberlandt, Ber. d. bot. Ges., 1886, p. 206 ; Moore, I.e. ; Oltmanns, 1. c.; 

 Kohl, Carotin, 1902, p. 103. According to Prillieux (Compt. rend., 1874, T. LXXVIII, p. 506),^ the 

 chlorophyllous plasma in certain leaf-cells of Selaginella Martensii forms masses which glide in' the 

 same way over the cell- wall. Cf. also Haberlandt, Physiol. Pflanzenanatom., 2. Aufl., 1896, p. 229. 



a Bohm, Sitzungsb. d. Wiener Akad., 1856, Bd.xxu, p. 479; 1859, Bd - xxxvn, p. 453; Stahl, 

 Bot. Ztg., 1880, p. 340 ; Schimper, 1. c., p. 225. 



8 de Bary, Bot. Ztg., 1877, P- 731- * Stahl, 1. c., p. 324. 



FIG. 54. Transverse section through the leaf of Lemna trisulca 

 (after Stahl). A. surface position (day position). B, arrangement 

 of the chlorophyll grains in intensive light. C, position assumed 



in darkness. 



