CHANGES IN CONTENTS OF STOMATA. IOI 



In table 49 is given a series of observations made in the year 1906 in March. 

 The data were entered in tabular form at once, and for the sake of convenience 

 and brevity a rough grading of the quantity of starch and oil present was 

 used, o meaning the absence and 1 a medium amount, and 2 the apparently 

 full amount. When it was difficult to decide readily the signs minus ( — ) 

 and plus ( + ) were used to modify the grading. 



The facts presented in this table indicate a slower opening movement and 

 a longer period of starch dissolution than is shown in the notes made in the 

 summer. I have attributed this difference to the lower temperature preva- 

 lent in March.* Making due allowance for such variation, due to this and 

 probably other causes, we may regard as beyond doubt the conclusion that 

 the starch and oil vary in amount, their quantitative fluctuations being com- 

 plementary to each other. The minimum starch content occurs during the 

 latter part of the morning, at the time when maximum 

 oil content occurs. Before and after this period the 

 amounts of starch and oil vary in inverse order. 



The diurnal movements of the stomata are such as 

 to lead to the suggestion that the variations of amount 

 of the starch and oil content are closely connected 

 with them. I have made an attempt to test this view 

 observationally in the following manner: As has been Fig. 32a.— Verbena cM- 



. . , , , r ,-. , t . ata, experiment 220. 



pointed out, the sizes of the stomatal openings are not 



uniform, and it thus happens that two adjacent stomata may be in quite 

 different physiological condition — the one open and the other closed. On 

 two occasions I have found one stoma quite closed and the other, very close 

 to it, widely open, at about 10 a. m. By applying iodine under constant 

 observation, the open stoma was found to possess distinctly less starch than 

 the closed stoma. Fig. 32a shows the difference in the size of the plastids, 

 due to different amounts of starch, in two neighboring stomata, 30 micra 

 apart, one widely open (12 micra), the other about one-third (4 micra) open, 

 taken from preparation at n h 30 m a. m., May 3, 1906. From this it would 

 seem that the above suggestion is sustained, as far as concerns the starch. 

 The evidence to be shown beyond does not, however, favor the same view 

 as regards the oil, the role of which remains problematical. 



* Observations made at the end of December, 1906, when the temperatures were still 

 lower, showed a still less active physiological condition of the guard-cells. 



