

1905.] On Vegetable Assimilation and Respiration, + 407° 
We will take first two special experiments with leaves of cherry-laurel in 
the open air, and subsequently one in which the leaf is in a glass chamber, 
sunk in a water-bath (the normal arrangement in our assimilation experi- 
ments). 
For the experiments in the open air, the cut leaf was pinned out by its 
margin on a small thin rectangular board which was hinged by its lower edge 
to a large rigid horizontal base-board. Through the thin hinged board was an 
oval opening, only a little smaller than the leaf, and over this the leaf was 
stretched. 
The stalk of the leaf dipped into a little well of water in the base-board 
and remained in the water at whatever angle the hinged frame might be 
sloped. A thermo-junction was inserted in the mid-rib of the leaf and the 
free ends of the wires hung down into mercury-cups on either side of the 
water-well. Supported in a hole through the base-board was a funnel which 
contained a thermometer and the control thermo-junction, and could be filled 
with water at any desired temperature. The whole of this part was carefully 
screened from solar or indirect radiation. The two junctions were connected 
up with one another aud with the galvanometer by wires running to mercury- 
cups in the horizontal board. 
- On July 17, 1904, the sun shone with unclouded brilliance throughout the 
day. A leaf was set up on the hinged frame and the following temperature 
observations were made by means of the galvanometer. 







. che Leaf- 
Hour. Conditions. temperature. 
A.M. aC, 
11.25. | Leaf in shade; shade-temp., 27° C. .................. 28 °0 
es _( Leaf vertical, facing south in direct sun. Bright eae 
ees 0) | mercury thermometer in sun, 30°°5 C. 39-3 
P.M. 
12.7 _ Frame inclined till leaf is normal to the solar 44°6 
| radiation 
12.10 ‘A glass plate interposed in front of leaf............... 44°3 
12.20 _ Glass plates also behind, above, and at sides, within 51:0 
| an inch of leaf, boxing it in 
12.25 Visible brown spot of killed cells. 
12.28 Sun-temp., 32° C. Front and top glasses off, others 44°5 
remaining 
12.35 All glass plates taken away...................sceeseeeees 41°4 
12.38 Leaf-frame placed vertically .....................0e eee. 39°0 
12.45 Large rectangular cell of water (temp., 23° C.) 41°8 
| close to leaf in front, leaf closed in behind, 
above, and at sides with glass plates 
Experiment ended as leaf is extensively turning 
brown, killed by the heating to 51° C. 


