ii 4 



THE PHYSIOLOGY OF STOMATA. 



Control: Guard-cell plastids appearing more granular than at 6 a. m., and smaller; 

 starch less in amount, but not very much difference; oil drops large; starch in chloren- 

 chyma plentiful. 



Experimental part: No starch in guard-cells or chlorenchyma; 2 to 6 micra; scarcely 

 one entirely closed. 



SUMMARY, BLUE LIGHT. 



In plants exposed to blue-violet light during the early part of the morning, 

 between the time of normal maximum and minimum starch content — - 



(1) The starch content of the guard-cells is reduced. 



(2) The oil is not formed. 



(3) Starch is not formed in the chlorenchyma. 



(4) The stomata open, but not so much as normally or as in red light. 

 When the experiment is started at the time of normal starch minimum — 



(1) The starch content increases in the guard-cells. 



(2) The oil is reduced to the minimum. 



(3) The starch content of the chlorenchyma decreases. 



(4) The stomata gradually close. 



With the exception of the smaller amplitude of stomatal movement as 

 compared with red or normal illumination, the course of events is normal 

 and is so as regards the behavior of starch. The failure to form oil in the 

 early part of the day is to be noted. 



6a.m. l st day lla.rn.6d.rn. 2° day lla.m.6a.m. 3 d day lla.m.6a.m. 6 th day lla.m. 



Fig. 39. — Effect of prolonged exposure to red (broken line) and to blue light on the amplitude of 

 stomatal movement. Verbena ciliaia. 



When the period of experimentation is extended over several days, the 

 gradual disappearance of starch from the stomata is to be noted, and this 

 may be referred to the generally starved condition of the leaf. Movements 

 of the stomata continue, however. They open toward 11 a. m. and gradu- 

 ally close toward evening. The maximum opening is, however, slowly 

 reduced (see fig. 39). 



