METHODS. 29 



leaf were taken, that the stomata in this were less open than in the epidermis. 

 This must, I feel sure, be attributed to the dilution of the alcohol by the 

 escaping water from the chlorenchytna of the leaf, since I have shown, con- 

 clusively I believe, that the absolute alcohol, when properly used, does the 

 work expected of it. Wilson & Greenman (1892) used absolute alcohol for 

 fixing the leaves of Melilotus, and believed that the stomata were fixed as 

 in the living condition, but these authors did not attempt to demonstrate that 

 this was the case. They may properly have been justified in believing that 

 the stomata were not shut, but, if found half open, they could not have been 

 sure that they had not been wholly so before treatment. Even this, however, 

 may be questioned, for Copeland (1902) found that "alcohol" (when applied 

 beneath the cover-glass, I presume) caused the stomata of certain plants 

 to close. I can believe that this was the result of the killing action in the 

 protoplasm of alcohol too dilute to fix the cell-wall. Farmer & Chandler 

 (1902), however, noted that in plants (Kalanchoe) treated with an excess of 

 CO 2 the stomata were gorged with starch and the guard-cells remained 

 open even when killed with "spirit." Those of the control plants were found 

 shut. 



In studying the contents of the guard-cells, the well-known methods of 

 Bohm (1856, potash and iodine) and of Meyer (1885, chloral hydrate and 

 iodine used together), as also the simple I + KI reagent, were used. Boiling, 

 as an additional means of swelling the starch granules, was employed. 

 Experience taught, however, that the simple iodine test was sufficient. 



The transverse diameter measurement given is the distance across the pore,* 

 that is, the opening between the bodies of the guard-cells and not the distance 

 between the ridges, inner or outer. 



EFFECT OF CAUSTIC POTASH UPON STOMATA. 



Incidentally to making certain other observations, it was found that the 

 stomata of Verbena, when subjected to boiling in water, often remained as a 

 result quite widely open, while those of a dead and dried leaf were not affected 

 in this way. This was attributed to the swelling of the starch, which might 

 be expected to produce a result simulating turgor by raising the internal 

 pressure of the cell. An attempt to produce a like result with potash obtained 

 an effect which was a great deal more striking. Stomata treated with strong 

 potash open remarkably (fig. 9) to an extent similar to that seen by Leitgeb 

 in the moribund stomata of Galtonia candicans. When, however, the stoma 

 has become widely open it then very suddenly closes, as with a snap, so that 

 unless one is actually observing the effect of the reagent the closed condition 

 only may be seen. 



*I have adopted Copeland's (1902) term and usage. 



