tmpar <- par( pty="s", mar=c(3.1,3.1,0,0), mfrow=c(1,2) )

mplot( cloning.means$pred, cloning.means$sd,
   group=cloning.means$clone, xlab="", ylab="" )
mtext( "(a) mean by clone identifier",1,2)
mtext( "clone SD", 2, 2 )

mplot( cloning.means$pred, cloning.means$sd,
   group=cloning.means$type, xlab="", ylab="" )
mtext( "(b) mean by type", 1, 2 )
mtext( "clone SD", 2, 2 )

par( tmpar )