

1905.] On Vegetable Assimilation and Respiration, © 413 
light and other varying factors very difficult at really high temperatures. 
These relations will form the subject of a separate communication. 
In the present work the temperature of the leaf rarely exceeds 30° C., and 
the duration of the individual experiments is usually not long, so that not 
much correction need be made for the time-factor. It will be mentioned 
when this becomes necessary. | 
It will be convenient to state for future reference what amounts of 
assimilation we shall take as maximal for the different temperatures con- 
cerned in this work. 
The data for cherry-laurel are to be found in “Assim. and Resp. III.” 
The final curve, given in fig. 6 of that paper, was smoothed out by free-hand 
to the curve C in fig. 2 of this paper. The data used for it represent the 
assimilation-values two hours after the initial moment of heating to the 
required temperature. The initial values will, at high temperatures, be 
greater, and their precise value depends partly on a hypothesis discussed. 
elsewhere.* These initial values are represented by the curve B, which: 
below 25° C. coincides with the other curve, C. 
The values for each degree of the curve C are set out below, being expressed 
in grammes COz, assimilated per 50 sq. cm. per hour. 
°C. “C. =e, al 63 
eee 00038 One 00065 AS ise 00103 Deas 00151 
The curve A represents the curve of initial assimilation-maxima for 
Helianthus. It is based on such observations in the present paper as are 
undoubtedly maximal. Four of these are above all suspicion, as follows :— 
| °C. 
Mx periment) X 5 scjsns cst yews 00090 at 18-0 
. BG eet oats: 00109 at 20-7 
. ene nena 0:0131 at 22°3 
<4 00290 at 30-0 
The values for the two leaves are fairly close together at 18° C., but at 
30°0 C. Helianthus has gone up out of proportion to cherry-Jaurel, 2.e., it 
has a larger coefficient of temperature-acceleration. 
* F. F. Blackman, “ Optima and Limiting Factors,” loc. cit. 
