Il8 THE PHYSIOLOGY OF STOMATA. 



The stomata, being less than half open at the beginning of the experiment, 

 remained so, though closures become more pronounced during 36 hours. 

 Placed, at the end of 36 hours, for 3 hours in diffused light, a measurable 

 though not a great amount of opening movement occurred, while the starch 

 was reduced. 



Experiment 221. Verbena ciliata, April ay-May 3, 1906. Twig in situ covered with an 

 olla, and irrigated; twig kept in dark for 6 days. Set up on April 27, 1907, at 6 a. m. 



April 30, 6 a. m. Oil drops small but normal; stomata closed, or a mere slit; starch 

 absent from chlorenchyma; starch present in guard -cells in meager but variable amount; 

 sometimes plentiful; three examinations; the last with KI + I, i /i6 oil imm., oc. 3. 



April 30, n a. m. Control (see experiment 219, p. 113). 



Experimental part: Starch in guard-cells absent or in very minute quantities; none in 

 chlorenchyma. 



May 3, 6 a. m. Oil drops as before, viz, small or not evident; no evidence of starch in 

 guard -cells or chlorenchyma; an occasional stoma 3 micra in diameter; others closed. 



Control: Starch abundant in guard-cells ; a little in the chlorenchyma. 



ii a. m. Control (see* experiment 219). 



Experimental part: No starch in the guard -cells or chlorenchyma. 



The following three experiments were carried out to determine especially 

 if oil accumulates in the guard-cells in the dark : 



Experiment 160. July 14, 1905. Taken at 6 h so m a. m., at which time no oil drops were 

 visible; starch in guard-cells in fine granules; 2 to 5, mean about 4; 2 to n; mean 

 about 6 to 7 micra (the latter piece had very large stomata). 



a . m- Control: Oil drops large; no obvious change in starch content; 8.5 to 14 

 micra. 



Experimental part: No oil visible, nor change in starch content; 2 to 6; 2 to 8.5; 4 to 8 

 micra. 



No oil was formed in the dark during the period when, under normal condi- 

 tions, this occurs. The similar amounts of starch in the control is shown 

 by other experiments not to be due to the absence of change in the amount, 

 but to the return, after the minimum, which occurs about 8 to 9 a. m., to the 

 increased, but not maximum amount. 



Experiment 168. Verbena ciliata, July 15, 1905. 



5^3O m a. m. Cuttings placed in the dark room. 5.5 to 8; 2.8 to 8.5 micra; no oil drops. 

 9 h 4o in a. m. Starch plentiful in guard-cells, but no oil drops; no starch in chlorenchyma; 

 2.8 to 7 micra, a few with openings 8.5 micra. 

 Control: 5.5 to 8.5 micra; oil present. 



Experiment 2020. Verbena ciliata, March 17, 1906. 



51130"! a. m. Cuttings placed in the dark room. Starch abundant in guard-cells; absent 

 from chlorenchyma ; DO oil in guard-cells. 



ii a. m. Control: Starch absent from guard-cells: abundant in chlorenchyma; oil drops 

 large in guard-cells. 



Experimental part: Starch present in guard-cells; absent from chlorenchyma; no oil. 

 (See experiment 2010.) 



