Lioyp: LEAF WATER IN GOSSYPIUM iT 
nearly their whole length at once, making a long narrow opening. 
Thus I find that the pore lengthens from 12 to 13.5 u in one Case, 
and from 9 to 10.54 in another, while the width reaches 1.8 and 
2 w respectively, these transverse measurements being applicable 
throughout the major portion of the length of the pore. Such 
stomata probably attain a relatively high diffusive capacity more 
quickly than young ones, in which pores, because of the flexibility 
of their edges, they attain their full length gradually. In the 
only series of preparations I have at hand the shortest pore I 
find is 4.5 long and 1 wide. Its index of relative diffusive 
capacity is 2.12. Assuming that in further opening its dimensions 
advance to 8.4 by I u (those of a similar stoma in the same prepara- 
tion) and then to 9 by 1.5 u, the indices would be, for these dimen- 
sions, 2.9 and 3.67, whereas an older stoma would have measure- 
ments such as 14 by 0.8 u, or 12 by 1.5 u, with the indices 3.35 
and 4.24, respectively. That is, for the same width of pore, the 
maximum length is reached much more rapidly and a relatively 
high diffusive capacity more quickly in older thai in younger 
stomata. If relations such as these obtain, as the evidence before 
us appears to indicate, we may well think that they may affect 
the rate of incipient drying,* either with or without appreci- 
able wilting. Differences of this kind may help to account 
for the results obtained by Bergen,t who found that the old 
leaves of sclerophyls transpire more than young leaves which 
have just attained their maximum area, though he further ob- 
served that the same relation holds for cuticular transpiration as 
well. In this regard, Pringsheim’s work, already referred to, 
may not be overlooked. It is to my mind doubtful, in view of 
the results on loss of leaf water presented in this paper, that the 
differences observed by Bergen} as between sun and ghade leaves 
depend upon the water carrying capacity of the vascular tissues. 
Turning to the data of TABLES I and IX, as represented in 
FIG. I, it becomes apparent that the sharp rise in leaf water be- 
tween the 6 and 8 hours neither harmonizes with the results given 
in the remaining tables, nor does the curve of stomatal openings 
* Livingston, B. E. 
t Bergen, J. Y. Di a tee cab Alors 
type. Bot. Gaz. 38: 446-451. D 1904. 
t Bergen, J. Y. Transpiration of sun leaves and shade leaves of Olea europaea 
sind other tidid Daseloeehgrebon. Bot. Gaz. 38: 285-296. O 1904. 
