PLATE 56 



A. — Late stage of development of host reaction to the invasion of Urophlyctis 

 alfalfae. Infections have taken place near the tip of a growing point. The division 

 of exterior cells has gone on extensively. The cells around the older portions of the 

 cavity formed by the fungus have also been stimulated to division. The vascular 

 bundle at the center of the mass of tissue has begun to produce parenchyma toward 

 which the fungus is inclined to direct its course. 



B. — Vertical section through a well-developed gall near its central axis, showing 

 its laminated structure arising from the thickening of bud elements. The cavities 

 containing the dark-colored spore masses are seen distributed through the tissue, a 

 condition that causes the mottled appearance of the interior of the living gall. 



