n6 the; physiology of stomata. 



Experiment 154. — Verbena, July 10, 1905. Cutting placed in the dark room at 8 h 55 m a. m. 



July 10, S h 55 m a.m. Starch in very small amount, appearing as minute granules in the 

 pale plastids; 5.5 to 10 micra. 



io h 30 m a. m. No increase of starch observable ; 2.8; 2.8 to 5.5 micra. 



Control: 2.8 to 7; 4 to 7; 2.8 to 5.5 micra. Little if any increase of starch observable. 



i h i5 m p. m. Small increase of starch; if anything more in the dark-room plant than in 

 the control. Abundant starch in the chlorenchyma of control, but in the experimental 

 plant no more than at 8 h 55 m a. m. ; 2 to 5 micra. A few extreme measurements: closed 

 and 5.5 micra; control, o to 3 micra. 



July n, 8 a.m. 2 to 5.5; o to 5 micra. Comparison with the control shows a distinctly 

 greater starch content in the guard-cells of the experimental plant. Experimental cutting 

 placed in strong diffused light at this time. 



II h 20 m a _ m . Closed; o to 3; o to 4 micra. The younger stomata are those chiefly 

 closed, while the mature ones are usually open to 2 to 4 micra. Very little starch in the 

 mature stomata, but considerable amounts in the young ones. The specimens taken turned 

 out to be rather young and had in consequence a large number of undeveloped stomata. 

 The large proportion of closed stomata is attributed in part to this. Starch granules in the 

 chlorenchyma quite obvious. 



Experiment 155. — July 11, 1905. Cuttings placed in the dark room at 8 h 35 m a. m. 



July 11, 8 h i5 m a. m. Control: Little starch in guard -cells; oil present. 



8 h 35 m a. m. Control: No starch in guard-cells; oil bodies at maximum; cuttings placed 

 in the dark; control pieces taken also from the cuttings showed no starch in guard-cells, 

 and oil drops large; starch in chlorenchyma; 4 to 9; 2.8 to 8.4; 2.8 to 8.4 micra. 



July 12, 8 h 5o m a. m. No oil drops; starch abundant in guard-cells in large granules, the 

 plastids appearing wholly stained with iodine; none in the chlorenchyma; o to 2.8 (7) 

 micra, 80 per cent closed ; o to 4 micra, 70 per cent closed. 



1 p. m. Starch still present in guard-cells. 



July 13, 8 a. m. Only an occasional stoma has starch; 90 per cent closed, the rest 

 open to a slit of 1 or 2 micra; no starch in chlorenchyma; in malformed guard-cells a large 

 amount of starch is to be found, and this is true also of perfect guard-cells when they are 

 paired with imperfect ones. Part of the material placed in the strong diffused light of a 

 north window at this time (8 a. m.) with the following results: 



9 h 45 m a. m., in diffused light. Minute granules have appeared in the chlorenchyma, 

 but none as yet in the guard-cell plastids. 



I2 h i5 m p. m. in diffused light. Stomata closed, save for a few which are opened to a slit 

 of 1 or 2 micra; the plant is partly wilted; stem trimmed; stomata of leaves which are 

 submerged in the water of the vessel in which the cutting stands are widely open, but no 

 starch is to be seen in them. 



3 p. m. in diffused light. Distinctly deeply-stained starch grains in the chlorenchyma; 

 a small amount in fine granules in the guard-cell plastids. 



6 p. m. Light. A distinct increase of starch in the guard-cell, though not abundant. 



July 14, 7 a. m. Part of experimental material, after 3 days in the dark room, has stomata 

 ranging from o to 4 micra in width, 50 per cent being 2 micra; starch content of guard-cells 

 varies from a little to abundance; none in chlorenchyma. 



Summary of 144, 154, and 155. — When material is taken at the time of 

 minimum starch content, maximum oil content, and maximum opening, and 

 placed in the dark the oil apparently does not reappear. Starch increases 

 during the first 24 hours, and shows a decrease at the end of 48 hours. In the 



