408 Dr. F. F. Blackman and Miss G. L. C. Matthaei. [Apr. 11, 








| Hour. Conditions. PEs 
temperature. 
P.M. “C: 
2.30 A new leaf set up. Leaf in shade. “4 
2.40 28-1 
2.45 Temp. in shade of chimney, 27°°3 C. (Sun-temp., | 28°1 
| 2.50 32° C.) | 28°6 
| 3.0 28°6 
3.10 Sun’s radiation reflected on to the leaf from plane | 33°0 
glass mirror | 
one Ditto, but water-cell in path of reflected rays ...... fT aaa 
3.22 Mirroriremoved: ).))2.7te eee ee renee be 2s. ate 28°4 
3.23 Water-cellrremoved',...... 222s te ese. ee Ze 28°2 
3.24 Mirror replaced without water-cell............... eee 30°1 
3.27 Substituted a mirror of thin glass ..................... 31:0 
3.30 Mirrorimemovedets:,/4..c:gsepe ees eee ete ee 28-0 
3.34 it ; 31°7 
3 36 eaf moved into direct sunshine, leaf vertical ...... { 33-6 
3.39 Leaf at right angles to solar radiation. Sun- 33°6 
| temp., 29°°4 C.; shade-temp., 26°-7 C. 
| 3.47 A cell full of water (25° C.), 1 inch in front of leaf 31:3 
| 3.50 All shaded with’ black clothpm. 353039) eee ee 26°6 
4.0 Leaf moved into shade, boxed in with glass plates. 28-4 
4.4 Shade-temp., 26°°3 C. 28°5 
4.6 Sun reflected by mirror on to boxed-in leaf in shade 36°5 
rs Back glass alone removed. Shade-temp., 25°:3 C. { aan 
4.27 Leaf vertical in direct sun with front glass on 33°2- 
alone 
4.33 Leaf boxed in by adding the other glass plates...... 42°6 
Experiment stopped. Shade-temp., 25°:2 C. 

We may sum up these observations as follows :— 
Hxpervments in Direct Sunshine. 
Excess of Internal Temperature of Leaf in Brilliant Sunshine over Reading 
of adjacent Bright Mercury Thermometer in the Sun. 


| Excess leaf- 
Hour. Conditions. t 
emperature. 
5 OF 
IN@ORiyctce hee Lieat werticalits cone eee cee ee eee oil 
ae ere ate ee eat normalato sums Tayse coq ete eae | 13—9 
ey Re act eee cae Leaf normal in’ glass chamber.7...-4.0-5---- 4-44. | 20 
i pe eh scene Ditto; belund water-celll (ee eases toe eee 10 
About 4. Pi,” 2. \sleats vertical eee ereerree ee BUN ibe 5 nt ae 25 
3 1.) Igéat- norms a0, SU earner ren. -< kecn eete ee eee 4 
rm 2. Ditto: behind watvelcellmenr rere s cerns see 2) 
oh ...| Leaf normal to sun, in glass chamber............ 14 



