survival probabilities from survival tree (rpart)

Hi!

How to compute probabilities of survival from rpart object?
Consider the following example:

library(rpart)
survtree <- rpart(Surv(time,status)~., data=aml)

This code will produce the following survival tree:

1) root 23 26.44184 1.0000000
  2) x=Maintained 11 12.61182 0.6848303 *
  3) x=Nonmaintained 12 10.81338 1.4426070 *

If I am not wrong the rightmost numbers are relative risks compared to whole 
population (e.g. root node). How to get survival probability function 
S(t|x)?

Regards,
Ludvik