create sequences from two "from" and "to" vectors

hi all,
how can I create sequences that start from a known vector, say x1 and end
with another say x2- also suppose all the sequences will be the same length.
I don't want to use a for loop
x1<-c(1,2,3,4); x2<-(3,4,5,6);
what I want is 
1 2 3 4 
2 3 4 5
3 4 5 6

Thanks

mapply(seq, x1, x2)