varieties of Sorghum (Rangaswami and Panduranga, 
1936). A papery condition which is apparently similar 
to that of papyrescent maize has been produced by two 
X-ray induced mutations in barley (Scholz, 1956). 
ACKNOWLEDGMEN'TS 
During the preparation of the manuscript, many help- 
ful suggestions were made by Professor P. C. Mangels- 
dorf of Harvard University. Professor Angelo Bianchi 
of Pavia University helped in the preparation of some 
of the slides. 
