128 COMPENDIUM OF GENERAL BOTANY. 



The physiology of the plienomeiia of movements will acquaint 

 us with adaptive movements which will bring the leaves into the 

 most suitable positions with reference to the sunlight. The chloro- 

 phyll-bodies themselves have special adaptations for the maxinmm 

 utilization of the sun's rays. 



(h) Movements and Changes in Form of Chlorophyll-bodies. 



According to Stahl, the chlorophyll-bodies among certain forms 

 of the so-called lower plants (iilamentous alga^) are capable of move- 

 ment. In Mesocarpus each cell j)ossesses a rotating chlorophyll- 

 plate which bisects the cell longitudinally. In diffuse sunlight the 

 flat surface is turned toward the light, while toward the rays of 

 direct insolation a profile position is assumed. In the single- 

 layered leaves of the moss Funaria hygrometrica the chlorophyll- 

 bodies assume a position along the lateral walls (profile exposure) in 

 direct sunlight as M'cII as in the dark, -while in the ordinary diffuse 

 sunlight they are adjacent to the outer walls (surface exposure). 

 In the palisade-cells of the higher plants it has been observed 

 (mainly according to Stahl) that the approximately hemispherical 

 chlorophyll-ljodies with their flattened surfaces directed toward the 

 cell-wall (longitudinal) extend, that is, elongate, somewhat more 

 into the interior of the cell in diffuse sunlight, while in direct sun- 

 light they lie more closely in contact with the cell-wall and increase 

 their diameter in the direction of the adhering surface. Covering 

 a leaf-portion with tinfoil causes this part to become more dark- 

 green as compared with the strongly illumined portions (Sachs). 



The following deductions may be drawn from the three phe- 

 nomena illustrated by the above examples, namely, the rotating of 

 the chlorophyll-plate, and the movements and change in form of 

 the chlorophyll-bodies: 1. Chlorophyll is enabled to derive a 

 maximum benefit from definite light-intensities by enlarging its 

 surface area. 2. It protects itself against light-rays of too great 

 intensity, very probably because it would thereby be injured in its 

 function and composition. According to Pringsheim, chlorophyll 

 is destroyed by concentrated sunlight in the presence of oxygen. 



(c) The Chemistry and Physiology of Chlorophyll. 



The exact chemical composition of the green coloring substances 

 designated as chlorophyll is but little understood. It contains the 



