  We have investigated the relationship between the morphology of helical
particles and the features of the cholesteric (N$^\ast $) phase that they form.
Using an Onsager-like theory, applied to systems of hard helices, we show that
the cholesteric handedness and pitch depend on both the pitch and the curliness
of the particles. The theory leads to the definition of pseudoscalars that
correlate the helical features of the phase to the chirality of the excluded
volume of the constituent particles.
