According to Hadley's ggplot book (p. 109), both the graphs below should have a legend, and yet none appears in my hands.  

Any suggestions?  I can't see a typo.  Is there a bug?

library(ggplot2)
data(LakeHuron)
huron = data.frame(year=1875:1972,level=LakeHuron)
p = ggplot(huron, aes(year)) +
  geom_line(aes(y= level - 5), colour = 'blue') +
  geom_line(aes(y= level + 5), colour = 'red') 
print(p)

key =  c('below' = "blue", 'above' = "red")
p = p + scale_color_manual("Direction", values = key)
print(p)

> sessionInfo()
R version 2.12.1 (2010-12-16)
Platform: i386-pc-mingw32/i386 (32-bit)

locale:
[1] LC_COLLATE=English_United States.1252 
[2] LC_CTYPE=English_United States.1252   
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C                          
[5] LC_TIME=English_United States.1252    

attached base packages:
[1] grid      stats     graphics  grDevices utils     datasets  methods  
[8] base     

other attached packages:
[1] ggplot2_0.8.9 proto_0.3-8   reshape_0.8.4 plyr_1.4     

loaded via a namespace (and not attached):
[1] tools_2.12.1
> 
# on Windows XP
> version
               _                            
platform       i386-pc-mingw32              
arch           i386                         
os             mingw32                      
system         i386, mingw32                
status                                      
major          2                            
minor          12.1                         
year           2010                         
month          12                           
day            16                           
svn rev        53855                        
language       R                            
version.string R version 2.12.1 (2010-12-16)
> 
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