10 



BEHAVIOR OF STOMATA. 



of stomatal apertures the number of measurements was usually 

 increased, when the agreement was invariably much better. 



Many objections have been raised to the stripping method since 

 its development by Lloyd, most of them made without sufficient 

 reason. The essence of the method is the almost instant dehydra- 

 tion by the alcohol and consequent hardening of the cellulose walls 



TABLE 2. 



of the guard-cells and surrounding epidermal cells, which fixes them 

 in the shape in which they were when plunged into the alcohol. The 

 dilution of alcohol in the cell-wall caused by the extraction of the 

 water within the cell is not sufficient to soften these walls or to cause 

 them to lose their form. The error, if error there be, must occur 

 during stripping or immediately following. The objection made by 

 Laidlaw and Knight that the jarring due to the operation causes 

 closure may be dismissed, for, if stomata of plants growing in the 

 open field closed each time they were jarred, they would be perma- 

 nently closed in a region of almost constant wind, such as the Great 

 Plains or the Great Basin. Moreover, stripping itself would make it 

 impossible to find any strips with open stomata. 



The more common objection that shrinkage and distortion occur 

 is to some extent true. A large number of strips were measured to 

 find the amount of this shrinkage, and it was found to be less than 1 

 per cent when it occurred at all. Immediately after stripping, the 

 width and length of the stripped area upon the leaf were measured 

 with dividers and compared with the length and width of the strip. 

 In most cases the shrinkage was not perceptible, but in the case 

 of wilted leaves there was very slight shrinkage. But as this was 

 always less than 1 per cent, the greatest error possible was not more 



