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The Castor bean can withstand the least amount of drought of any of the 

 plants observed. After being subjected to drought for one week, there was a de- 

 cided change in general appearance. The leaves wilted and shrivelled, and the 

 stalk was not turgescent enough to remain erect, but wilted. It was almost impos- 

 sible to obtain the epidermis from the leaf because of its clinging to the under- 

 lying tissue. By referring to the accompanying drawings of the Castor bean 

 (Plate 9) the diSerences in structure of the plants grown under the different con- 

 ditions may be seen. The stomatal guard cells and the surrounding tissue cells 

 are seen to be smaller in plants subjected to drought. The stomata are increased 

 in number from 500 per inch in moist air to 700 per inch in drought. 



A cross section of the stem showed the characteristic difference in turgidity 

 and size of the cells. 



The effect of drought on the cucumber in general is to destroy the turgescence 

 and give the stem a wilted appearance. The number of stomata are increased in 

 drought, as seen in figure 10. 



From the above experiments it may be seen that immature plants subjected 

 to drought for only a short time have decided changes in general appearance and 

 structure. It seems very probable that in different plants such changes might 

 occur, as a result of drought, as would greatly change not only the habits of the 

 plant but its life history. 



