310 L. A. GIDDINGS 



upper ones are sessile and clasping. This arrangement gives 

 the plant a broad, spreading surface below, but an exceedingly- 

 reduced one above. 



THE STOMATA 



Microscopic observations were made on the number of stomata 

 per unit area at different heights and of different parts of the 

 same leaf. It was found that as a rule the number of stomata 

 increased with an increase in the height of the leaf and also 

 toward the tip of the leaf. In the following observation, which 

 serves as a type, three leaves were used; one from a height of 

 18 cm., one from a height of 65 cm., and one from^ a height of 

 100 cm. In examining the leaves for stomata, pieces of the 

 epidermis were shaved off from both the upper and lower sur- 

 faces near the base, near the middle, and near the tip of the leaf. 

 To bring out more clearly the comparison of the number of sto- 

 mata in the leaves at different heights and in different parts of 

 the same leaf, table 1 has been compiled. In this table the 

 maxima, the minima, and the average number of stomata per 

 square centimeter of leaf area, as determined by ten counts in 

 each place, are given. The area of the lowest leaf in this case was 

 379.7 sq. cm., of the second leaf 215.2 sq. cm., and of the third 

 leaf 65.1 sq. cm. These areas include both surfaces of the leaf. 



The average number of stomata per square centimeter of sur- 

 face for the lowest leaf was 10,634; for second leaf 12,775; and for 

 the highest leaf 13,487. The data obtained in this observation 

 correspond very closely with those from other similar observations 

 though there were minor variations as would naturally be ex- 

 pected. The smallest average number found on the upper 

 surface of any leaf was 7825 per square centimeter, and the 

 gi'eatest average number was 12,966. The smallest average 

 number found on the lower surface was 9258, and the greatest 

 average number was 16,220. In the specimens studied there 

 was practically no difference in the size of the stomata of the 

 different leaves. 



Transverse sections of the leaves showed that the epidermis 

 was always heavily cutinized; the stomata were not sunken to 



