Smithsonian Report, 1919. — Coville. 
Plate 17. 
Blueberry Leaf Exuding Sugar from Glands Interpreted as Osmotic-Pressure 
Safety Valves. 
This is 
two gianas on the midrib atthe ham of thesocond and fourth lateral veins above thesiigar tlroi>sho\\Ti 
nearthemiddleofthe picture. Thisexudation of sugar isinterpreted as a means of relief from excessive 
internal pressure that might burst thecells of the plant or derangeits physiological activities. 
