
1905.| On the Physiological Processes of Green Leaves. 43 
Finally, if we assume that starch or «ulin is the synthesised product, 
having the formula C,H,,0,, then one part by weight of carbon dioxide can 
give rise to 0°613 parts of the carbohydrate. 
_In considering which factor we ought to take for calculating the increase in 
dry weight of the leaf from the amount of carbon dioxide fixed, we must bear 
in mind that the question is quite independent of the nature of the primary 
product of assimilation, and turns on the relative proportion of the above 
three classes of carbohydrates at the close of the experiment. 
In two separate determinations of the starch and sugars of leaves of 
Tropeolum majus in full assimilation, Brown and Morris found* them 
apportioned as follows, the determinations being expressed as percentages on 
the dry weight of the leaves. 
y i 
So ECG) ae ere er 3°693 0425 
Came-sOal ..ecc.cares 9°980 7330 
WDJOMELOSO, <. 4. .c0 ee cee a8 0:000 0:000 
ee VlOS6 4.0. ccuec cases. 1:410 Pasa 
IVEAWGOSE: 9.5.28 osha 2250 2°710 


Total per cent. ... 17°383 17-575 
By multiplying each one of these values by the factor appropriate to the 
particular class of carbohydrate as stated above, we obtain average values as 
follows :— 
Factor deduced from lL ~..2...:. 0642 
Ego ce: 0640 
” 2” 
These are not far removed from the arithmetical mean of the three values 
for the three different classes of carbohydrates, which is 0°646. 
The “carbohydrate-factor” we have used for converting carbon dioxide 
assimilated into its equivalent by carbohydrate is 0-640. 
Since 1 c.c. of carbon dioxide at normal temperature and pressure weighs 
000196, the number of cc. given in Column (7), Table I, multiplied by 
(0°00196 x 0°640) should give the corresponding weight of carbohydrate produced 
in one square decimetre of leaf per hour. These values are shown in the last 
column of Table I. 
Before drawing any conclusions from the above results as to the rate of 
assimilation in ordinary air of the usual carbon dioxide-content, we will give 
the details of a further set of experiments in which the air supplied to the 
leaf-cases had been previously enriched with a further determinate amount 
of that gas. 
* © Journ. Chem. Soc.,’ 1893, Trans., p, 671. 
