Mary had to leave Howard before completing her degree.

This was a setback, though not a permanent disqualification from intellectual life — the Depression truncated the formal education of many people who went on to distinguished careers.

But it meant that Mary would build her inventive career without the credential of a university degree, in a world that placed great weight on such credentials.

She eventually enrolled at what is now the University of the District of Columbia, where she took courses that interested her.

She also studied floriculture — the cultivation of flowers — at the local level, eventually operating a flower shop that became one of her primary sources of income.