par(mfrow=c(1,2),mar=c(4,3.1,0,0.6))

attach(ntukey)
margin.plot(lat,y,geno,xlim=c(95,105),error="red",xlab="",ylab="",
   xpos=103.5,ypos=100, mod="")
mtext("(a) lat marginals by geno",1,2)
mtext("height",2,2)
margin.plot(lat,y,geno,orient="switch",error="red",xlab="",ylab="",
   xpos=115,ypos=100, mod="")
mtext("(b) geno marginals by lat",1,2)
detach()

par(tmpar)