434 Dr. F. F. Blackman and Miss G. L. C. Matthaei. [Apr. 11, | 
principles as that of normal leaves, but it is more feeble throughout; it is 
instructive to note that its maxima at 26° C. and 32° C., viz., 0°0103 and 
0°0139, bear such a ratio to one another as to indicate that this leaf has a 
somewhat smaller coefficient of temperature acceleration than a normal leaf. 
If so, the feeble leaf would differ from normal cherry-laurel leaves in just 
the same way as the latter differ from leaves of Helianthus (cf. Section V1). 
Experiment XII (August 1, 190+4)—Cherry-laurel; Weight, 1°79 grammes ? ; 
Area, 60 sq. cm.; Current Rate, 800 cc.; COs = 2:1 per cent. 







(average). : 
| Real 
pos CO, Oeb assimilation 
Exposure. | Time. ture of lied absorbed ih 
| leaf. cg at by leaf ae 
| " | per 50 cm?. 
| 
A.M, i 
Leaf exposed to whole 9—10 26 *2 Prelimjinary 
diffuse light plus half 
sunlight (angle incid. 10—10.30 26 ‘0 0 ‘0318 0 0053 0 0103 
= 60°) 
F Heated 
10.30—11 39 0 
11—11.30 32 ‘0 0 :0308 0 :0063 0°0131 
Whole diffuse light plus | 11.30—noon 32 °0 
whole sunlight (angle 
incid. = 0°) noon—12.30 P.M. 32 °0 0 -0320 0 0068 0 0139 
P.M. 
Whole diffuse light plus | 12.3830—1 32 ‘0 
half sunlight (angle 
incid. = 60°) 1—1.30 32 °0 0 0350 0 0064 0 :0133 




This leaf was so placed at first that the sun’s rays fell on it obliquely with 
an angle of incidence = 60°, ze, the sunlight was of only half its full 
intensity; the collective diffuse light fell on it unimpeded. When the leaf- 
temperature was 26° C. the assimilation was only 0:0103 instead of 0°0121 
(the normal maximal value for 26° C.). The day was very bright and sunny, 
and this clearly is the maximum for the temperature. That this is so was 
proved in the second reading when, with the same intensity of light (the 
chamber being continually readjusted to the angle of 60°), raising the 
temperature of the bath sent the assimilation up 25 per cent. 
At about 32°C. the value obtained is 0:0131, very nearly or approaching 
maximal. Next the light isin its turn increased by adjusting the chamber 
normal to the sun’s rays so as to double their intensity, and the temperature 
is kept down still to 32°C. There is only a small increase of assimilation 
and that may possibly only be due to unrecorded increase of temperature. 
