plot of sp SpatialPolygonsDataFrame: col not working?

Dear list,

I'm plotting polygons with:
displayDataset(GDAL.open("G:/PERU/imorm2007/test1TNT/PC1_3s.tif"))
plot(boundary,lwd=2,col=2,add=T)
plot(pols.ferns3,col=3,lwd=1,add=T)

(cannot use spplot because I need the add=T)
but the polygons are actually black, ignoring col. I think that this is
because the boundaries of the polygons get displayed in black, 
regardless of the filling color, and my polygons are very narrow at this 
scale (which is the one I need). Is there any way of changing the color 
of the boundaries or just not displaying boundaries?

Thanks!

Agus

Dr. Agustin Lobo
Institut de Ciencies de la Terra "Jaume Almera" (CSIC)
LLuis Sole Sabaris s/n
08028 Barcelona
Spain
Tel. 34 934095410
Fax. 34 934110012
email: Agustin.Lobo at ija.csic.es
http://www.ija.csic.es/gt/obster