218 STUDIES IN PLANT REGENERATION 
with which potato leaves so planted produced roots and, for a long 
time nothing else, caused the writer some astonishment (Fig. 10, а). 
d, with 
. 
, 
Fic. то. Series of regenerating leaves of potato ( Solanum tuberosum). a, showing regeneration of roots only ; 0, drawn 
from the under side showing swelling at the end of the petiole containing starch; с, swelling and roots present 
true tuber at the base. 
At last а series was found in which the phenomenon described by 
Knight fecurred (Fig. 10,4). Several leaves showed gradations 
between this type of regeneration and the preceding one in that 
