a numeric value specifying the side where the axis is
plotted: 1: below, 2: left, 3: above, 4: right.
root.time
the time assigned to the root node of the tree. By
default, this is taken from the root.time element of the
tree. If it is absent, this is determined from the next option.
backward
a logical value; if TRUE, the most distant tip from
the root is considered as the origin of the time scale; if FALSE,
this is the root node.
...
further arguments to be passed to axis.
Author
Emmanuel Paradis
Details
The further arguments (...) are used to format the axis. They
may be font, cex, col, las, and so on (see
the help pages on axis and
par).