20, 2 Trelease: Foliar Transpiring Power of Coconut 169 
markedly from day to day, it seems reasonable to regard these 
averages as representing what may be expected to be the general 
course of the daily march of transpiring power for these plants 
at this season of the year. 
TABLE 1.—Fluctuation in the index of foliar transpiring power of Cocos 
nucifera, as indicated by standardized cobalt-chloride paper, and varia- 
tion in apparent pinna width, together with evaporation data. 
[Relative values show percentage of range from lowest to highest values.] 
3 Evaporating power 
Observation. ing: power ower Aven width. peta Some 
+: meter). 
No. Time. | Actual. | Relative.| Actual. | Relative.| Actual. | Relative. 
a.m.p.m, mm 
Pie ae 6 0.56 100 33.4 
\ Hr eda einen dearer re 7 0.52 bf. f Meeee ane Pagan 0.8 28 
Bes: ces yaanee 8 0.52 87 32.6 58 1.3 45 
LE RA es SO ie es a 9 0.58 90 |.- Se 1.9 66 
| [oe Seen eens eee 10 0. 52 87 31.3 25 2$ 79 
Rp ace AOR ae eee EE 11 0.49 Lif en I eeipeea ele, 37 98 
Pcs ee 12 0.46 67 30.3 i) 2.8 97 
BS es 1 0. 45 oh eat are eagle Roe 2.9 100 
Se ee eee seu eee an 2 0.44 60 30.9 15 2.8 97 
Sa See eee 8 0.42 i. 7 93 
|b Pee resem Sch ae 4 0.389 43 31.2 23 2.4 83 
ee a 5 0. 40 47 il 19 66 
13. 6 0.38 40 32.2 48 0.6 21 
oo eee 7 0.36 38 0.5 17 
15 - 8 0.35 30 2.8 63 0.3 10 
1 ee as 10 0.27 3 34.3 100 0.1 3 
17 12 0.27 8 34.3 100 0.0 0 
in 2 0.26 0 84.3 100 0.0 0 
5G eo re ae 3 0.38 23 ---- 
ER Bos a 4 0.36 38 34.2 98 0.0 0 
1 Re 2 Reins S Geae eee Sie 5 0.52 87 aie 0.1 3 
= Be go eR 6 0.54 98 83.8 0.4 14 
* Cubic centimeters per hour for preceding hour. 
As has been pointed out by Copeland,(5) there is a strand of 
colorless, thin-walled cells running along each side of the midrib 
on the undersurface of the coconut pinna, and these strands 
act as hinges. When the leaves are well supplied with water, the 
hinge cells are distended and the two pinna wings are held far 
apart; but when there is a progressive deficiency of water in the 
hinge cells, the wings of the pinna revolve downward, about the 
Pinna midrib as an axis, so that their lower faces approach 
each other. The angle of divergence between the two pinna 
wings may be approximated by measuring the distance between 
184350-——_4 
