[R] How to show which variables include in plot of classification tree

[Muhammad Subianto]

Dear all
For my research, I am learning classification now.
I was trying some example about classification tree pakages, such as 
tree and rpart, for instance,
in Pima.te dataset have 8 variables (include class=type):

library(rpart)
library(datasets)
pima.rpart <- rpart(type ~ npreg+glu+bp+skin+bmi+ped+age,data=Pima.te, 
method='class')
plot(pima.rpart, uniform=TRUE)
text(pima.rpart)
summary(pima.rpart)

In the result I found only 5 variables: npreg, glu,  bmi, ped, and age 
were showing in the plot.
Now, I have 50 variables in my dataset. The result my classification 
tree very difficult to know which
variables showing in the plot. Are there any trick which variables are 
showing in plot.

Thanks for your help.
Muhammad Subianto