RicE: INTERNAL SORI OF PUCCINIA SORGHI 49 
such different conditions are also linked by reference to the activi- 
ties of reproductive maturity. 
It is by no means sufficiently clear just what is involved in 
our conception of reproductive maturity but these cases of spore 
formation in abnormal and non-adaptive positions certainly 
emphasize its importance in determining both structural and 
functional modifications. 
It is a pleasure to acknowledge the assistance of Dr. Robert 
A. Harper of Columbia University in work upon this problem. 
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