Problem with a barplot...

Hello,

I'm having a bit of a problem with a plot, and I'm hoping that someone might
be able to help.  I'm running the R Cocoa Gui v1.12 on OS X 10.4.2, and I'm
doing a stacked bar plot.  The plot itself is quite simple:

barplot(as.matrix(s.strats.in),main="Strategy when strong", col=strat.col)

where s.strats.in is a matrix with a number of rows that define the height
of each stacked bar.  However, ever since I expanded the number of columns
from 100 to 500, the borders of the bars are overwhelming the plot (the bars
are proportionally smaller, and thus the colours are getting muddied by the
black borders).  Changing the border colour doesn't help at all, and I was
hoping that there was a way to remove the borders of the bars (i.e. have
each bar snug right up against the next).  I've tried varying any parameter
that seems to have the slightest relation, but no luck.

Can someone point how to remove the borders or perhaps suggest an equivalent
way to do this with another function?  I would appreciate any and all help.