[R] plot(linear model) without lines

[cryan at binghamton.edu]

running R 2.5.1 on WinXP.

plot(model formula here) produces 4 useful residual diagnostic plots.  Two questions about them:  

1.  How can I isolate just one of the four, and have only that one be shown?  str(plot(model)) didn't give me any insight.

2.  How can I make the lines (I guess they are lowess lines) not appear on the plots?

Thanks.

--Chris Ryan