[R] hclust doesn't return merge details

[Arne Neumann]

 Dear R-users,

I tried to receive the merge details of a clustering by using the
summary function of hclust.
For illustration I use the Longley data as done by Prof Ripley (Wed 11
Apr 2001)
d <- dist(longley.y) 
d <- d/max(d) 
hc <- hclust(d, "ave") 

But instead of getting a matrix for $merge I get:
>summary(hc)
		Length Class  Mode     
merge       30     -none- numeric  
height      15     -none- numeric  
order       16     -none- numeric  
labels       0     -none- NULL     
method       1     -none- character
call         3     -none- call     
dist.method  1     -none- character

Am I missing something?
Arne Neumann

> R.version
platform i386-pc-mingw32
arch     i386           
os       mingw32        
system   i386, mingw32  
status                  
major    1              
minor    7.1            
year     2003           
month    06             
day      16