328 



LOCOMOTORY AND PROTOPLASMIC MOVEMENTS 



tion by placing 

 upon the outer 



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- 



themselves 

 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 

 mediterranean ; , 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. XII, p. 418. Wittrock observed 

 (Stahl, I.e.) that the chlorophyll plates of Gonotonema reacted similarly. 



1 Frank, Jahrb. f. wiss. Bot., 1872, Bd. vni, 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, I.e.; 

 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. 



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

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



3 de Bary, Bot. Ztg., 1877, P- 73 1 - ' Stahl > ' c -.- P- 3-4- 



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. 



