PLATE 28 



Blueberry leaf exuding sugar from glands interpreted as osmotic-pressure safety 

 valves. 



This is a leaf of the highbush blueberry, Vaccinium corynibosum. The photograph 

 was taken May 19, 1916. The sugar-secreting glands, sometimes called extra-floral 

 nectaries, are situated in this plant on the back of the midrib and along the margins 

 of the leaf, toward its base. The drops of sugar solution have been wiped away from 

 the glands on the left-hand margin and from two glands on the midrib at the base of 

 the second and fourth lateral veins above the sugar drop shown near the middle of 

 the picture. X 4. 



