PLATE 45 



A. — Cross section of midrib of mature plants (Magnum Bonum), showing abnormal 

 development of the vascular tissue with thickenings of the walls of the phloem 

 adjacent to the fibers. X 130. 



B.— Cross section of petiole of mature plant, showing abnormally large development 

 of the vascular tissue of the petiolar wings. X 130. 



