  We present here a study of the Halpha equivalent widths of the flocculent
galaxy NGC 4395 and the grand design galaxy NGC 5457. A difference between the
mean values of the Halpha equivalent widths for the two galaxies has been
found. Several hypotheses are presented in order to explain this difference:
differences in age, metallicity, star formation rate, photon leakage and
initial mass function. Various tests and Monte Carlo models are used to find
out the most probable cause of this difference. The resultsshow that the
possible cause for the difference could be a variation in the initial mass
function. This difference is such that it seems to favor a fraction of more
massive stars in the grand design galaxy when compared with the flocculent
galaxy. This could be due to a change of the environmental conditions due to a
density wave.
