PLATE lo 



A. — Section of cabbage tumor after seven days, showing the chains of cells beginning 

 at the epidermis and areas of small cells in active division in the center of the leaf. 



B. — Section of cabbage tumor after two weeks' gro%vth. The epidermis has been 

 broken at the top, and infection may occur. Some sclerenchymatous cells with thick 

 lignified walls have developed in the center of the tumor. 



