IN VEGETABLE BIOLOGY. 201 
It should be mentioned that Von Mercklin * had as early as 1850 
noticed variatious in the position of chlorophyll, but without 
attributing them to any physical agency. Shortly after Bohm, 
Gris f figured and described arrangements of chlorophyll grains 
round the nucleus, sume of which must have been the effect either 
of light or its absence, although this was not realized by him; 
Indeed the research had a quite different object. Gris also 
figured the protoplasm of etiolated plants from which the chlo- 
rophyll has disappeared, as collected upon the cells' side-walls or 
in their corners. To Famintzin I belongs the credit of ascer- 
taining displacements of chlorophyll to be the effect of illumi- 
nation and not of heat; in a species of Mnium this author found 
that the grains come out on the free (surface) walls in light, and 
in darkness pass on to the side-walls. Shortly after this, two 
memoirs were published by Borodin $, in the first of which it was 
Shown that the chlorophyll grains of prothallia, collected by 
sojourn in darkness on the side-walls (“ Nachtstellung "), move 
on to the surface-walls (“ Tagesstellung ") in three hours, 
the reverse movement coming first into view not until after 
twenty-four hours’ withdrawal from light. Moreover, Nacht- 
stellung and Tagesstellung were likewise noticed in many Mosses, 
in the propagula of Marchantia polymorpha, and in other Hepa- 
tice. Borodin’s second memoir, devoted to Phanerogams, marks 
a decided advance, since in it the effect of the intensity of light is 
first distinctly noticed ; he showed that the chlorophyll of insolated 
leaves of Lemna trisulca, Callitriche verna, and Stellaria media is 
first driven upon the side-walls, butif the sunlight be still allowed 
to act, the grains collect in heaps in the corners of the cells. Boro- 
din proved that this is due to light and not to heat, inasmuch as the 
Movement will not take place in light composed of the less refran- 
gible rays of the spectrum, but it will if,without any change of tem- 
perature, only rays of high refrangibility be used. Besides this, 
Borodin showed that the chlorophyll of the above types passes on 
to the side-walls in darkness (in the thicker portion of Lemna 
frisulca on to the wall separating the two layers as well as on to 
the side-walls); and also that this assumption of Nachtstellung 
* * Beob. an. d. Prothallium d. Farrnkräuter.” 
t Ann. d. Sc. Nat. Bot. 4™° série, tome vii. (1857). A 
t Bull. Acad. d. Sc. de St. Pétersbourg, 1867 ; reproduced in Pringsheim’s 
Jahrb, f. wiss. Bot. Band vi., and translated in Ann, Sc. Nat. 5"* série, tome vil. 
$ Bull. Acad. d. Sc. de St. Pétersbourg, 1868 and 1869 (xii. and xiii). 
