242 SUMMARY OF CURRENT RESEARCHES RELATING TO 



BOTANY. 



A. GENERAL, including the Anatomy and Physiology 

 of the Phanerogamia. 



a. Anatomy.* 

 CI) Cell-stiaicture and Protoplasm. 



Influence of Light upon Protoplasmic Movement-!— Mr. S. Le 

 M. Moore has further investigated the phenomenon that chlorophyll- 

 grains alter their position, collecting into masses in sunlight, and 

 moving on to the side-walls of the cells, the latter movement being 

 effected also, but more slowly, in darkness. These displacements of 

 chlorophyll are the effect of illumination and not of heat. Frank gave 

 the name of " epistrophe " to the distribution of the grains upon the 

 free walls and the parts of the wall bordering on intercellular spaces, 

 and that of " apostrophe " to the arrangement upon the side-walls. He 

 also confirmed the statements of his predecessors that epistrophe is more 

 quickly assumed after apostrophe than vice versa. Apostrophe produced 

 by strong illumination Moore proposes to call " positive," tbat produced 

 by weak illumination " negative." 



To the whole of these phenomena Mr. Moore applies the term 

 " photolysis," and proceeds to discuss the question whether the grains 

 of chlorophyll are drawn passively along with the streaming plasma, or 

 whether they have the faculty of independent motion. The question 

 was answered in the former sense by Sachs, and Frank and Pfeffer are 

 of the same opinion. On the other hand, Prillieux looks upon the 

 movement as resulting from the attraction of one grain upon another, 

 and of the cell-wall upon the grains. Velten considered that the 

 grains have some power of moving independently of the protoplasm. 



The author gives three reasons which have led him to declare in 

 favour of Sachs's theory. As to the movements of chlorophyll- grains in 

 the dark, the results obtained under this head are thus summed up : — 

 (1) The epistrophized grains of sun-loving plants are negatively apo- 

 strophized after a few hours in darkness. (2) Negative apostrophe is very 

 slow in making its appearance in aquatic types. (3) Negative apostrophe 

 can be induced in sun-loving plants in low light. (4) The effect of 

 continued darkness upon grains already apostrophized is to drive them 

 into masses in the corners, or, more rarely, upon the side-walls of 

 the cell. (5) Still longer exposure to darkness may cause many, if not 

 all, of the grains to come out on to the free walls. (6) Positively 

 apostrophized grains of sun-lovers remain in apostrophe on removal to 

 the dark. 



The author proposes to term the whole range of possible grades of 

 illumination from darkness to direct sunlight the photrum, and that 

 portion of the scale which will be powerful enough to change the chloro- 



* This subdivision contains (1) Cell-structure and Protoplasm; (2) Other Cell- 

 contents (including Secretions); (3) Structure of Tissues; and (4) Structure of 

 Organs. 



t Journ. Linn. Boc. Loud.— Bot., xxiv. (1887) pp. 200-50 (1 pi. and 3 figs.). 



