We investigate star formation along the Hubble sequence using the ISO Atlas of Spiral Galaxies .
Using mid-infrared and far-infrared flux densities normalized by K-band flux densities as indicators of recent star formation , we find several trends .
First , star formation activity is stronger in late-type ( Sc - Scd ) spirals than in early-type ( Sa - Sab ) spirals .
This trend is seen both in nuclear and disk activity .
These results confirm several previous optical studies of star formation along the Hubble sequence but conflict with the conclusions of most of the previous studies using IRAS data , and we discuss why this might be so .
Second , star formation is significantly more extended in later-type spirals than in early-type spirals .
We suggest that these trends in star formation are a result of differences in the gas content and its distribution along the Hubble sequence , and it is these differences that promote star formation in late-type spiral galaxies .
We also search for trends in nuclear star formation related to the presence of a bar or nuclear activity .
The nuclear star formation activity is not significantly different between barred and unbarred galaxies .
We do find that star formation activity appears to be inhibited in LINERs and transition objects compared to H II galaxies .
The mean star formation rate in the sample is 1.4 M _ { \sun } yr ^ { -1 } based on global far-infrared fluxes .
Combining these data with CO data gives a mean gas consumption time of 6.4 \times 10 ^ { 8 } yr , which is \sim 5 times lower than the values found in other studies .
Finally , we find excellent support for the Schmidt Law in the correlation between molecular gas masses and recent star formation in this sample of spiral galaxies .