We propose several tests of the idea that the electron is fractionalized in
the underdoped and undoped cuprates. These include the ac Josephson effect
and tunneling into small superconducting grains in the Coulomb blockade re
gime. In both cases, we argue that the results are qualitatively modified f
rom the conventional ones if the insulating tunnel barrier is fractionalize
d. These experiments directly detect the possible existence of the chargon-
a charge e spinless boson-in the insulator. The effects described in this p
aper provide a means to probing whether the undoped cuprate (despite its ma
gnetism) is fractionalized. Thus, the experiments discussed here are comple
mentary to the flux-trapping experiment we proposed in our earlier work.