[R] suppress some boxes drawn by legend(,fill)

[Tom Boonen]

Is there any way suppress box color and frame of a box drawn by
legend(,fill)? I am able to suppress the color, but not the frame (see
the example below). Many thanks! (This follows up from a question
asked on the list in 2006 by Florian Koller)

Tom

x1 <- rnorm(100)
x2 <- rnorm(100, 2)
hist(x1, main = "", col = "orange",ylab = "density", xlab = "x", freq
= F, density = 55,xlim = c(-2, 5), ylim = c(0, 0.5))
par(new = T)
hist(x2, main = "", col = "green", ylab = "", xlab = "",axes = F, xlim
= c(-2, 5), ylim = c(0, 0.5), density = 45, freq = F)
abline(v = mean(x1), col = "orange", lty = 2, lwd = 2.5)
abline(v = mean(x2), col = "green", lty = 2, lwd = 2.5)
legend(3, 0.45, legend = c("x1", "x2", "mean(x1)", "mean(x2)"),
       col = c("orange", "green"), fill=c("orange","green", 0, 0),
       lty = c(0, 0, 2, 2), merge = T)