20, 3 McLean and Lee: The Citrus-canker Organism - 819 
ture of the stomata of the mandarin orange is such as to exclude 
water, thus preventing the ingress of the canker bacteria. The - 
structure of the stomata of the grapefruit is such as readily 
to allow the ingress of water on the surface of the leaf, thus 
st “ 
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Fic. 2. A, B, and C, stomata of Szinkom mandarin orange, X 570: A, surface view; B, 
median cross section; C, underview. Showing ridge of entrance, r; outer chamber, 0; 
pore, p; and dorsal wall of guard cells, d. D, E, and F, stomata of Florida seedling 
grapefruit, X 570, showing same parts as A, B, and C. 
permitting the entrance of the canker bacteria. Text fig. 2 
shows these stomatal differences; the figure is taken from the 
senior writer’s paper previously mentioned.° 
*McLean, Forman T., A study of the structure of the stomata of two 
species of Citrus in relation to citrus canker, Bull. Torrey Bot. Club 48 
(1921) 101-106. 
