The supplementary systems envisaged above will be usually two-dimensional, and these two dimensions usually will be correlated closely with intrinsic color and luminosity; however, it is crucial not to require such a correlation. In each particular case, it is of prime importance to the autonomy of the particular situation that the most ``natural groupings'' of the spectra be followed - no matter what the physical situation may later turn out to be.
Some of the supplementary systems may incorporate specimens over a great range of intrinsic color and luminosity; others may be located in a limited area of the HR diagram.
In a great majority of the new systems the defining ``boxes'' will resemble the MK boxes in including only spectra that resemble each other closely. However, in the ``baskets'' such as that containing He I 3888 stellar-wind spectra, a wide variety will be found; but one very interesting fact will be true for the inhabitants of each basket: they will share one outstanding, particular characteristic in common with other specimens in the same basket.