  The mass distribution of dense cores is a potential key to understand the
process of star formation. Applying dendrogram analysis to the CARMA-NRO Orion
C$^{18}$O ($J$=1--0) data, we identify 2342 dense cores, about 22 \% of which
have virial ratios smaller than 2, and can be classified as gravitationally
bound cores. The derived core mass function (CMF) for bound starless cores
which are not associate with protostars has a slope similar to Salpeter's
initial mass function (IMF) for the mass range above 1 $M_\odot$, with a peak
at $\sim$ 0.1 $M_\odot$. We divide the cloud into four parts based on the
declination, OMC-1/2/3, OMC-4/5, L1641N/V380 Ori, and L1641C, and derive the
CMFs in these regions. We find that starless cores with masses greater than 10
$M_\odot$ exist only in OMC-1/2/3, whereas the CMFs in OMC-4/5, L1641N, and
L1641C are truncated at around 5--10 $M_\odot$. From the number ratio of bound
starless cores and Class II objects in each subregion, the lifetime of bound
starless cores is estimated to be 5--30 free-fall times, consistent with
previous studies for other regions. In addition, we discuss core growth by mass
accretion from the surrounding cloud material to explain the coincidence of
peak masses between IMFs and CMFs. The mass accretion rate required for
doubling the core mass within a core lifetime is larger than that of
Bondi-Hoyle accretion by a factor of order 2. This implies that more dynamical
accretion processes are required to grow cores.
