b4 
its usefulness under unfavorable circumstances, and under them the lack 
of continuity becomes too great an objection; in addition, the observations 
demanded at short intervals on several pinne at once require a dangerous 
haste in manipulation. This method is serviceable where immediate 
results will answer, as, for example, in testing the effect of shading. Esti- 
mates of the total daily transpiration by this method, based on determi- 
nations made in the sun, run higher than those just given—sometimes as 
high as 75 liters per diem. 
After this necessarily prolonged discussion of method, a brief consid- 
eration of the relative transpiration from the upper and nether surfaces 
of the leaves, the influence of their age on their transpiration, and the 
effect exerted: from without by the illumination and the wind will be 
possible. 
Almost the entire transpiration of the coconut is through the stomata 
of the nether surface of the leaf. In experimenting on the transpiration 
from the upper surface, and at no other time, have I found it necessary 
to seal the edges of the glass slides to prevent interference by the moisture 
of the atmosphere; of course, it was also necessary to guard against the 
passage of moisture from the nether surface to the upper. These pre- 
cautions being taken, it requires at least six hours of continuous sunshine 
to enable the cobalt paper to change color. Tf the leaf is placed in the 
shade or in the dark, the hydration is somewhat slower. On January 21, 
a day when there were occasional clouds, the average time of reddening, 
when the paper was placed against the lower surface, was eleven minutes, 
but against the upper, seven hours; this interval, from 9 a. m. to 4 p. m., 
was required for the change; and paper blue at 11.25 was still of the same 
‘color at 5.30, but red at 8. 
Experiments were made on the transpiration of leaves which were just 
full grown, those about six months older, and those a year beyond matu- 
rity. Two series of determinations were undertaken with the individuals 
of each age. These varied in detail, as is true with all of this work, but 
the relation was constant—the leaves six months beyond maturity trans- 
pired rather less than those which had just grown, while those a year old 
were decidedly the most active of all. For example, the total transpira- 
tion for seven hours, from 9.20 a. m. to 4.20 p. m., February 14, was— 
Grams. 
Mature leaf cccccicsecccsccccdeccsoessce-ceescosseeccccnecesccncnsnneccennessseoenseseremerenetecns 2.70 
Six mMOnths OIGEL....-.-.::-------------------cccscges--ceeee-ceccceeneeceneemerecnceesenenesoncs 1.68 
Ome year O1der.............-.--c.cecccccesseesesseseeceeeeeseenenenennenenstnensensesenenentes 3.37 
The result for the leaf of mean age is too small; this is due to its being 
the first to become greatly abnormal. The totals for 43 hours, from 1.50 
to 5.20 p. m., February 15, were— 
Grams 
Mature leat. ...........:--ccccccssesseeeeeecenssceqcscceceecennsccccccenenseqeesennescesanenesnness 0.78 
Six months older..........-.-----------:------ssscccecsceeeeeescerereceeceasennsettoosacneeneses 75 
One year UA cols faceted Meceslesliciia decannoniesdn cates hduaindcssasemensteanesdepoes®® 1.50 
