93 pringsheim's researches on chlorophyll. 



trace of it. The first striking change in such a case is stagna- 

 tion of rotation, with which is associated an irregular aggre- 

 gation of the protoplasm at the insolated area which hinders 

 the movement. Upon this follows an extending destruction of 

 the cell-content. The green chlorophyll-corpuscles through- 

 out the non-illuminated portion fall into disorder, lose their 

 arrangement in rows (fig. 24), and swell in a manner 

 commonly seen in them when they escape from the cell ; they 

 change their polyhedral or oval form and become, by the ab- 

 sorption of water, transformed into vesicles such as Goppert 

 and Cohn describe,^ and their contents, hitherto hardly recog- 

 nisable, now appear sharply circumscribed. Finally, the 

 protoplasmic utricle separates from the cell-wall, and all the 

 signs of death from light are apparent. In the insolated part 

 the chlorophyll-corpusc'es exhibit none of these changes, 

 nor does the protoplasmic utricle separate from the cell-wall; 

 and this portion may remain in this condition for months, long 

 after the adjacent chlorophyll-corpuscles have disintegrated. 



If before death is set in and before the chlorophyll- 

 corpuscles are completely decolorised the light be inter- 

 rupted, then the partly or almost entirely decolorised chloro- 

 phyll-corpuscles separate from the utricle and fall into the 

 rotating protoplasm, and with the formed elements circulate 

 uninterruptedly in its current, forming often small heaps of 

 corpuscles without disturbing the rotation, and though they 

 gradually lose colouring matter, and after a time are quite 

 colourless, they suffer no further change in form or substance. 

 By degrees in this way the insolated part becomes deprived 

 of chlorophyll-corpuscles and may get quite bare of them, 

 and Nitella-ceWs in this condition may be kept for months 

 unchanged, the rotation continuing vigorous, and the formed 

 elements in the protoplasm and the chlorophyll-corpuscles 

 in the non-illuminated area retaining their normal form, 

 colour, and arrangement (fig. 23). 



In other cases, again, if the action of light is of a high inten- 

 sity, and the insolated area is decolorised without the rotation 

 being stopped, there are often developed, especially in long 

 cells and when the insolated area is in the middle of the cell, 

 two currents instead of one, which rotate at opposite ends 

 of the cell, each independent of the other, and separated 

 from one another by the insolated area, which is a barrier 

 to the movement. 



But this action of light is not confined to green tissues. 

 Non-green cells — for example, the blue-sapped hair-cells on 

 the stamen of Tradescantia virginica — are affected in the 

 ' 'Bot. Zeit.,' 1849, p. 681. 



