268 



BOTANY 



PAKT i 



The movements of orientation of the protoplasmic body are usually 

 so gradual as to be only recognisable through their operations. They 

 are induced by changes in the external influences, especially as 

 regards the intensity of the light, and result in producing a definite 

 position of the protoplasmic bodies, as, for example, the orientation 

 of the chlorophyll grains with regard to the light. Movements of 



T 



FIG. 221. Streaming protoplasm 

 in the hyphse of 7tfii :'v<> <;// <'- 

 cans. ( After J. C. ARTHUR.) 



this kind have been most frequently 

 observed in Algae, in submerged Duck- 

 weed (Lemna trisulca), in the prothallia 

 of Ferns and Mosses ; but similar move- 

 ments can also be observed in the higher 

 plants. 



Kin. ~2'20. Varying positions taken by 



the Chlorophyll grains in the cells of In the cells of the filamentous Alga Meso- 

 I*mna triscvlca in illumination of dif- carpus, the chloroplasts, in the form of a single 

 ferent intensity. T, in diffuse day- kte sus ded length-wise in each cell, turn 

 light; S, in direct sunlight; N, at * \ 



night. The arrows indicate the direc- u l (On thelr longitudinal axes according to the 

 tion of the light. (After STAHL.) direction and intensity of the light. In light of 



moderate intensity, according to STAHL'S ob- 

 servations, they place themselves transversely to the source of light, so that 

 they are fully illuminated (transverse position) ; when, on the other hand, they 

 are exposed to direct sunlight, the chlorophyll plates are so turned that their 

 edges are directed towards the source of light (profile position). A similar pro- 

 tection of the chloroplasts against too intense light, and their direct exposure, 

 on the other hand, to moderate illumination, is accomplished, where they are of a 

 different form and more numerous, by their different disposition relatively to the cell 

 walls. In moderate light the chlorophyll bodies are crowded along the walls, which 



