Notes. ^(a)The ensembles identified by the first break in Fig. 3-bottom are called small-scale ensembles (SEs), and the ensembles identified by the second break are called large-scale ensembles (LEs) (see Sect. 4.2). ^(b)For SEs, the fragmentation level is defined as the number of fragments associated with each SE. For LEs, the fragmentation level is defined as the number of SEs associated with each LE. The uncertainty in the fragmentation level is assumed to be the Poisson error (). ^(c)The mass and (H₂) density were derived from the 1.3 mm low-resolution continuum data with a uv range of 9 ~ 910 kλ, and they are consequently independent of the 1.3 mm high-resolution data that we used to identify fragments (with a uv range > 910 kλ). ^(d)The Jeans lengths and masses were derived from the densities of SEs and LEs, estimated assuming a temperature of 200 K. ^(e)L_typical is the median separation between every two subobjects within each ensemble, and M_typical is the median mass of subobjects within each ensemble. The errors correspond to the median absolute deviations. For SE4, SE5, and LE2, there are only two subobjects within each ensemble, therefore, there are no median absolute deviations for them, and their errors were only estimated from the uncertainty of the distance to W51 IRS2 (5128 ± 1867 pc).