422 Dr. F. F. Blackman and Miss G. L. C. Matthaei. [Apr. 11, 
‘niaximum for 20°5 C. is 0-0088 ‘(see ‘p. 413), from which it follows that the 
‘amount of’ assimilation is not limited by the temperature, but ‘by the dulness 
Experiment V (July 22, 1904)——Cherry-laurel; Weight, 1:80. grammes ; 
Area, 55 sq. cm.; Current Rate, 800 c.c.; COs = 2:4 per cent. (average). 
Leaf-chamber adjusted Normal to Sun throughout the Day. 










Tempera- | Tempera- CO CO, acs eee 
Time. Illumination. ture of ture of ty gq. | absorbed a ni 
bath. leaf. on ose by leaf. 1. sEenveweme 
per 50 cm”. 
P.M. R a | 
11.40—12.40 _— | 19°0 == Prelimjinary | 
12.40—1.40 | Dull, cloudy sky ...; 19:0 20 °5 0 0392 0 0070 | 0 0073 
1.40 —2.40 5 . sl) 188 20 0 0 0384: 0 -0062 | 0 0065 
2.40—3.10 | Clouds less heavy...| 19:2 Ziti 0 0192 0 0037 0 0077 
3.10—3.40 | Sun coming out ...) Heated to 
29 -0 
3.40—4.25 | Bright sun for most 29 -0 Variable, ( | : 
of estimation 26°3 = |35 *8—31°5 fo mae polsa DS! 








of the illumination. In the final reading the value obtained, 00190, is the 
standard maximum for 33°7 C.,* which is about the average observed 
temperature of the leaf. Here, then, the assimilation, in spite of its 
magnitude, is yet limited by the temperature and not by the light, which is 
quite superfluously bright (as will be precisely demonstrated in Section V). 
It is interesting to note that the excess of the leaf-temperature over the 
bath-temperature gives a rough measure of the intensity of the incident 
light-radiation. The successive values 1°5 C., 1°2 C., 1°9 C., and 5°2 to 
6°°8 C., vary parallelly with the assimilation. 
Experiments VI and VII exhibit mixed effects of varying illumination and 
temperature, and frequent records of both were taken in order to see how far 
the assimilation values could be explained in detail by these data. We will 
take first Experiment VI, in which each reading lasted an hour, and the 
temperature and illumination were noted every 10 minutes. The details of 
these are given in the schedule of the experiment, and graphically in fig. 4 
The significant averages are given in Table I on p. 424. 
The day was dull and cloudy; continuous sun about 2 to 3 P.M. only. The 
assimilations fall short of maximal throughout the day. As the chamber was 
* Or for 33° C., as this is an early reading ; see p. 412 on influence of “ time factor.” 
