XYLARIACEAE 



229 





Fig. 91. Ophiobohts cariceti, cause of take-all of wheat. A. Spermogonium 

 in section. Speimatia are pear-shaped and curved. B. Portion of initial of 

 perithecium. The hyphae make a loose aggregate, in the center of which 

 are coiled ascogonia with deeply staining cells. C. Mature perithecium, in 

 diagram, lying obliquely and entirely immersed within the tissues, except 

 for the tip of the beak. D. Mature ascus. The asci are extruded intact 

 during wet periods and collect in a mass at the tip of the beak. (A and B 



adapted from Jones.) 



