56 Dr. H. T. Brown and Mr. F. Escombe. [Jan. 9, 
Table VII.—Rate of Assimilation deduced from Half-leaf weighing 







Method. 
| Increase in 
Time of Area in Dry cry eta 
Species of plant. megan | square weight in pac 
in hours. centimetres.) grammes. - 
per hour, in 
grammes. 
(1) 3/8/98.— 
| Catalpa bignonwides— 
A. Before insolation...... —— PATS) ak Pass — 
B. After insolation ...... 7:0 276°8 1°3488 0:°00791 
(2) 9/8/98.— 
Catalpa lignonioides— | 
A. Before insolation...... — | 225°6 0-9729 — 
B. After insolation ...... 5:0 | 1944 0-°9740 0-01370 
(3) 16/8/98.— | 
Catalpa bignonioides— | 
A. Before insolation...... a 418°35 1°8546 -— 
B. After insolation ......, 3°25 438° 45 2°1812 0:01660 
(4) 2/6/98.— 
Sparmanma africana— 
A. Before insolation...... — 150-0 0°6303 — 
B. After insolation ...... 6°25 150°0 0°6636 0°00387 
(5) 3/6/98.— 
Sparmanna africana— 
A. Before insolation...... | — 125-0 0°5086 — 
B. After insolation ...... 6:0 125-0 0°5287 0:00268 
| (6) 22/6/98.— 
Sparmanma africana— 
A. Before insolation...... — 125°0 0°4295 — 
B. After insolation ...... 6°5 125°0 0°4734 0°00540 


N.B.—In Experiments (4), (5), and (6) equal areas were cut from the two 
halves of the leaves before and after insolation. In the other experiments the 
entire half leaves were taken. 
In the results recorded up to this point we have seen that the general 
tendency of the Sachs’ weighing method is to give a much higher estimate of 
the rate of assimilation of leaves in ordinary air than is given by a method 
based on the measurement of the actual intake of carbon dioxide. The justice 
