  We examine the suggestion that most of the hot plasma in the Sun's corona
comes from type II spicule material that is heated as it is ejected from the
chromosphere. This contrasts with the traditional view that the corona is
filled via chromospheric evaporation that results from coronal heating. We
explore the observational consequences of a hypothetical spicule dominated
corona and conclude from the large discrepancy between predicted and actual
observations that only a small fraction of the hot plasma can be supplied by
spicules (<2% in active regions, <5% in the quiet Sun, and <8% in coronal
holes). The red-blue asymmetries of EUV spectral lines and the ratio of lower
transition region (LTR; T<0.1 MK) to coronal emission measures are both
predicted to be 2 orders of magnitude larger than observed. Furthermore, hot
spicule material would cool dramatically by adiabatic expansion as it rises
into the corona, so substantial coronal heating would be needed to maintain the
high temperatures that are seen at all altitudes. We suggest that the corona
contains a mixture of thin strands, some of which are populated by spicule
injections, but most of which are not. A majority of the observed hot emission
originates in non-spicule strands and is explained by traditional coronal
heating models. However, since these models predict far too little emission
from the LTR, most of this emission comes from the bulk of the spicule material
that is only weakly heated and visible in He II (304 A) as it falls back to the
surface.
