Bu!. 1417, U. S. Dept. of Agriculture 



Plate 8 



n 



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Longitudinal Sections of Alfalfa Roots 



A, Single Ozonium strand, with the central hyphse missing (X 162). B. Formation of the 

 mycelialweft and the entrance of the hyphal wedge between the first two rows of cork cells 

 (X 156).' C, A later stage than B. showing a well-developed wedge (X 175). D, Invading 

 hyphse between the cork cells and invading the cork cambium and some of the parenchyma 

 cells. Note the difference between the hyphse making up the wedge and those breaking 

 down the cortex. The cork cambium is beginning to collapse, the first indication of a 

 depression being visible. Entrance in this instance was effected through a lenticei. 

 The engulfed lenticei cells can be seen in the fungous accumulation (x 109) 



