  A radix sort tree arises when storing distinct infinite binary words in the
leaves of a binary tree such that for any two words their common prefixes
coincide with the common prefixes of the corresponding two leaves. If one
deletes the out-degree $1$ vertices in the radix sort tree and "closes up the
gaps", then the resulting PATRICIA tree maintains all the information that is
necessary for sorting the infinite words into lexicographic order.
  We investigate the PATRICIA chains -- the tree-valued Markov chains that
arise when successively building the PATRICIA trees for the collection of
infinite binary words $Z_1,\ldots, Z_n$, $n=1,2,\ldots$, where the source words
$Z_1, Z_2,\ldots$ are independent and have a common diffuse distribution on
$\{0,1\}^\infty$. It turns out that the PATRICIA chains share a common
collection of backward transition probabilities and that these are the same as
those of a chain introduced by R\'emy for successively generating uniform
random binary trees with larger and larger numbers of leaves. This means that
the infinite bridges of any PATRICIA chain (that is, the chains obtained by
conditioning a PATRICIA chain on its remote future) coincide with the infinite
bridges of the R\'emy chain. The infinite bridges of the R\'emy chain are
characterized concretely in Evans, Gr\"ubel, and Wakolbinger 2017 and we recall
that characterization here while adding some details and clarifications.
