209 



of drought on the trichomes caused the plant to become exceedingly viscous, giv- 

 ing the plant a glistening appearance. Another effect of drought on the general 

 appearance of the plant ^yas the prevention of the opening of the flower buds, 

 which soon withered. 



In the case of the plant kept under normal conditions for the same length of 

 time the le_^ves expanded perfectly, the leaf stalks were much elongated and quite 

 flexible. The plant was of lighter green color, and in general did not show the 

 dwarfed appearance of plants subjected to drought. 



When examined with a microscope the different tissues are found to show as 

 marked differences as the general appearance of the plants. 



When we compare two strips of epidermis, one taken from the lower surface 

 of the leaf of the plant grown under normal conditions and one from a plant sub- 

 jected to drought; the first difference noticed is that of the turgescence of the 

 plant cells. 



The cells of the plants grown under normal conditions are very large and 

 turgescent. 



The cells of plants subjected to drought lack turgescence, and show a weak, 

 flaccid cell wall, are also much smaller than these under influence of moisture. 

 The growth of the cells being retarded, the stomata are brought nearer to each 

 other so that the number per inch is 1400, while the number under normal con- 

 ditions is only 400 per inch. 



Drought also causes a slight change in the guard cells, producing a 

 corresponding change in the breadth of the stomata. 



See figures I and II. 



The trichomes of Oxalis are numerous and are of the glandular variety. 

 Their distribution over the surface of the leaf corresponds to that of the stomata. 

 On the epidermis of plants subjected to drought the trichomes are more numerous 

 than those of plants grown under moist conditions; are also shorter and more 

 globular. 



The cells of normal jilants contain an abundance of starch ; under the influ- 

 ence of drought this starch is greatly diminished. 



The Canna was the next plant observed, and was if possible more changed by 

 drought as regards manner of growth than the Oxalis. The plant was only sub- 

 jected to drought for three weeks, but in that short time the growth was consider- 

 ably retarded. 



When the seeds of the Canna are allowed to germinate under conditions of 

 drought, the plantlets grow very slowly, sending out numerous opposite leaves. 

 When the plants were removed to good conditions for growth, they refused for 



