An Impregnable 
Fortress 
Noie the size and 
offensive or defensive 
‘quality of the spines that 
protect this chestnut bur. 
No bird or squirrel could 
hope to penetrate such an 
array of bayonets. Such 
aspecimen, obviously, 
would not be among those 
chosen to carry forward 
an experiment in breeding 
the spines off the 
chestnut bur.” 
