385 
Sunlight upon Aquatic Plants. 
1. 5 minutes’ exposure to about 6 S; chloroplastids pale greenish 
yellow, rotation absent or very slow, and in io min. more rapid, but 
occasional cells die and rotation ceases. After i hour tested with 
bacteria, weak power of assimilation, absent or doubtful in parts 1 . 
2. Cell showing one rotation per 25 sec. after min. in 5 S, 
rotation slows to 55-60 sec. per revolution 2-3 min. after exposure ; 
then in 5 min. begins to quicken, and in 10 min.= 35 sec. per revolu- 
tion, in 20 sec. original rate. Chloroplastids slightly paler. 
3. No alum-solution, 1 min. exposure stops active rotation, 
chloroplastids quite green. After 1 hour still no rotation, but 
apparently a weak evolution of oxygen ; but careful examination shows 
that the movement of the bacteria continues in the darkness, and that 
many semi-anacrobic bacteria are present, and are attracted by the 
nutritious fluids evolved from the dying cells. Using bacteria from 
a young and well-aerated culture, no evolution of oxygen can be 
detected, and after 5 hours cells are no longer plasmolysable and 
replasmolysable. 
4. (a) With alum-solution, light = 4 S; after 15 min. exposure 
chloroplastids partially bleached, feeble rotation, which become active 
after J hour in weak light. 
( b ) Light =4 to 6 S ; after 15 min. rotation almost ceased, begins 
to recover in 5 min., and is quite active again in 15. Chloroplastids 
more or less bleached. 
(<r) Closed-cell-preparation. Owing to increased heating effect 
rotation ceases in nearly all cells after 5 min., recovering again in 
5-15 min. if only a part of the leaf was exposed. After 10 min. 
exposure, permanent stoppage, cells die, but the chloroplastids are not 
bleached (deficient supply of oxygen). 
5. ( a ) Light = 8 S, rotation ceases in 5-6 min., chloroplastids 
quite pale, and in 6-8 min. quite colourless, no recovery. After 
5 min. exposure the cells mostly recover, rotation recommences in 
J to 1 hour, and after being in diffuse light for 2-3 days paler exposed 
patch can no longer be distinguished from rest of leaf. 
(b) Without alum-solution, rotation ceases in 3-4 min., chloro- 
plastids still yellowish green, recovery in many cases but not in all. 
1 Longitudinal strips are most suitable for examination. The Bacteria were 
obtained from well aerated putrescent fluids (See Kny, Ber. d. D. Bot. Ges. xv, 
1897, p. 388), but the utmost caution is necessary with such impure cultures, and 
were it not that the results here given are simply confirmatory of previous ones, no 
mention would be made of them. 
