nucleus font collection for X.

You'll have to add /usr/X11R6/lib/X11/fonts/nucleus
to your X font path by either:

$ xset fp+ /usr/X11R6/lib/X11/fonts/nucleus
$ xset fp rehash

or by adding it to your X-server configuration file (usually
/etc/X11/XF86Config) and restarting the X-server.