68 , BOTANICAL GAZETTE [JULY 
to a change in the permeability of the chromatophores, thus allow- 
ing the phycoerythrin to diffuse out into the cell contents. The 
larger cells of the plant show this diffusion of the pigment before 
smaller cells at the tip show any such change. The change in color 
is most evident after the plant has been left standing at room tem- 
perature for 6-10 hours after removal from the constant tempera- 
ture chamber. Branches which remained the normal color after 
heating were found to proliferate and grow to some length when 
allowed to stand, while those which showed diffusion of the coloring 
matter from the chromatophores did not grow further. This fact 
justifies the use of the color reaction as an indicator of the duration 
of life. Table I expresses the average results of a number of 
experiments. 
TABLE I 
Temperature Duration of life Mean temperature 
(centigrade) (minutes) coefficient for 1° C. 
cooley gael topes i 300-340 320 
Reet sot 
Bas ce ees ic te 240-285 202.5 
hes i243 
B0 0c oe 210-255 249.8 
aes 1.16 
SE eee ore 185-215 200 
a cs Pe eae eee meee a eae Fis 
BF eS race ae EN 160-185 172°5 
TER 2:75 
Oh EERE HD SURI ie 75- 85 80 
re ae 
EY Seer eae ge ae 60- 75 67.5 
Pees 4 1.42 
ke Re ee 4O- 55 47.5 
ele .58 
os ae p A 5 30 
ves 234 
BF i 2-16 14 
peed 1.64 
1 gee SEE a en 7-10 8.5 
Average temperature coefficient for 1° C., 1.47. 
The temperature coefficient of the duration of life of Ceramium 
tenuissimum has been determined thus for the temperatures 
28-38° C. inclusive, and found to average 1.47 for each degree 
centigrade rise in temperature. This average temperature coeft- 
cient corresponds closely with that found by GoopsPrED (1.27), 
whose experiment involved the use of much higher temperatures 
