26 
was found: when 3000 M.C.S. was administered (500 M.C. ~ 658.), 
in one of the 6 experiments a faint response was observed; with 
4000 M.C.S. (1000 M.C. x 4S) all 5 cells show a distinct response. 
For 64 M.C. therefore the threshold hes between 3000 and 4000 M.CLS., 
ve. at + 3500 ALCS. 
Next there were applied in the dark 2000 M.C.S. (500 MC. X 4 S), 
256 M.C.S. (64 M.C. x 4S), 32 MCS (8 M.C. x 4S), 4 MCS. 
(1 M.C. x 4S) 1/,.M.C.S. (*/, M.C. x 48S), */,, MACS. (*/,, M.C. x 5S) 
and determined at what points of time these quantities are threshold- 
values. Moreover the threshold-value was determined for complete 
dark-adaptation. We had noticed that this was a good deal lower 
than the smallest quantity (‘/, M.C.S.) which was used before (see 
Licht u. Wachstum 1). 
The limit or threshold-value for the photo-growth-response of these 
cells adapted to the dark is at about */,,, M.C.S. This is a quantity 
much smaller than was hithertho used for stating vegetative reac- 
tions. By smaller quantities a reaction was sometimes perceived, but 
in the dark the limit is very difficult to fix, because with strongly 
decreasing quantity of stimulation the effect of growth decreases 
but slowly, about according to the cube-root of the quantity of 
stimulation (see L. u. W. I, which point we will further develop). 
So it already appears that the cell in the dark is + 350.000 times 
more sensitive for the light-stimulus than when adapted to 64 M.C. 
Table IV gives a survey of the process of adaptation from 64 M.C. 
to the dark. 
_ TABLE IV. Process of adaptation or increase of sensitiveness 
after discontinuance of exposure to 64 M.C. 
Limit | Erpel en of 
| sensitiveness 
In 64 M.C. + 3500 M.C.S. 1 
after 5 Min. 2000 =, 1.75 
( 13 Min. 
» 18 Min. Oey 13.6 
10% Min. 
„ 28}/2 Min. 32 nag 109 
12/2 Min. 
„41 Min. 4 875 
» 14 Min. 
„jan Min iam o2 7000 
15 Min. 
» 70 Min. cy a 56.000 
Adapted to the dark +%o , 350.000 
(after 90—120 min.) 
