
1905. ] On Vegetable Assimilation and Respiration. 425 
of it due to direct sunlight becomes more and more obliquely incident, so that 
the leaf-excess-temperature falls from 5°6 to 0°-6 C., bringing a steady fall of 
assimilation. The bath is, however, kept up to about 19° C. by circulating 
water, so that the leaf-temperature cannot fall as fast as the illumination, and 
the assimilation shows a larger and larger deficit below the maximum.. The 
whole experiment exhibits the assimilation as a function of the illumination, 
and not limited by the temperature. | 
_ Experiment VII, on the contrary, shows the assimilation as a function of 
the temperature ; it was a brighter day, and the leaf-chamber was continually 
adjusted normal to the sun’s rays. 
Experiment VII (July 23, 1904)—Cherry-laurel; Weight, 1-72 grammes ; 
Area, 52°5 sq. cm.; Current Rate, 800 cc.; CO2.= 2:1 per cent. 
(average). 
Leaf-chamber adjusted Normal to Sun throughout Day. 












| 
Real 
! Tempera- | Tempera- CO, Pear 
‘Time. Illumination. ture of ture of oe d absorbed geno 
bath leaf eee by leat. eesuom, 
j : per 50 cm’. 
A.M. s : 
8.20—9.20 | — — — Prelim|inary 
9.20—9.50 | Fairly bright sun ...) 19°3 25 0 0 0165 0 0054 0 :0117 
9.50—10.20 10.3—10.9, heavy | 18°5 21-2 | 
cloud ; 10.12, bright 18 ‘9 21°9 : 0 -0172 0 0045 00095 | 
sun; then dull 18 °8 21°3 | 
10.20—10.50| 10.27, faint sun; 19-0 22 °2 
10.36, bright sun; 19 °6 27 °°2 00181 0 0052 0°0115 
10.42, brilliant sun 20 °1 29 °2 
/10.50—11.20/11, bright sun;/f 201 30-1 : 
| 11.15, cloudy { 19 6 23 °7 } Ps dea 
11.20—11.50 | Cloudy.................. aor 22 °3 0 °0181 0 0042 O ‘0091 
11.50 a.mM.— | Heavy clouds ......... 1s) 4 21°3 0 :0146 0 -0041 0 -0088 
12.20 P.M. 
P.M. 
12.20—12.50 | Heavy clouds ......... 19 °3 20 °6 0 0184: 0 -0036 0 -0076 




The readings only last half an hour each, and the temperature and illumi- 
nation were recorded every three minutes throughout the experiment, so that 
full data for a careful analysis are available. The following table exhibits 
the significant numbers and averages :— 
