18 Lioyp: LEAF WATER IN GOSSYPIUM 
for the hours of observation bring out the relations between these 
and loss of leaf water in sufficient detail. That there should 
have been increase in leaf water in the amount of about 7 per cent. 
during the period (6 to 8) when the stomata were opening from 
0.7 to 1.4m, must have been due to meteorological conditions, 
though it is still not clear why the maximum leaf water had not 
been attained by the 6 hour, unless it should be shown that such a 
condition does not always intervene even in the early morning 
hours before sunrise. 
The flatness of the curve of stomatal opening after the 8 hour, 
it is likely, does not properly represent the facts, since from the 
evidence in TABLE xX there was probably a considerable opening 
and closing between 8 and 10, with the maximum diffusive capacity 
reached at about g. If, aside from this, the curve of stomatal 
opening is true, it would seem to indicate that the loss of leaf 
water from 300 to 240 per cent. took place without a sufficient 
amount of wilting to involve closure of the stomata, and that the 
leaf therefore had not passed beyond the condition of drying 
incipient to wilting. As no observations were recorded to test 
the truth of this conclusion and no measurements of the meteoro- 
logical conditions beyond the note that there was a general haziness 
until the 10 hour were made, we perhaps may be permitted to 
draw the lesson, that in such studies it is of utmost importance 
that the integral effect of such conditions should be known before 
any adequate interpretation of the water relations of the plant 
may be had. At present the most efficient method to this end 
is that of measuring evaporation with the blackened porous 
cup.* Ina future paper it is proposed to display the results which 
have been obtained in field studies of cotton in the light of such 
integration. 
Reference has been made above to the daily wilting of the 
leaves, observable at first at about the 9 hour. The stomatal 
measurements would seem to indicate that after this hour there 
is a rather steady closure. It therefore would be of importance 
to determine at what hour the maximum transpiration rate occurs 
when these conditions prevail. In anticipation of such determina- 
* Marinos B. E. A radioatmometer for comparing light intensities. Plant 
Wor : 96-99. Ap 1911; Light intensity and transpiration. Bot. Gaz. 51: 
aa D tort. 
