Question

Observation of your slant after another 24 hours may be necessary if you did not see endospores initially. why

Answer 1

The observation of a slant after 24 hours is necessary because even if you were not able to see any endospores previously, they might be present there. And incubation of 24 hours allows those spores to germinate, and you will be able to see the microbial growth in the slant.