[R] axis labels vertically

[BoM DS]

Hi,

I have a plot and a custom axis labeling, e.g.

  x<-c(...) 
  plot(x,axes=FALSE)
  axis(2)
  axis(1,1:50,c("label1",...,"label50"))

now since the labels are quite long, only a few fit on the page.
Can I rotate each label by 90 degree counterclockwise 
(so that they are vertical)