From the Washington Evening Star, April 28, 1926: "Miss Louise Thorne of the National Academy of Sciences holding a plant growing in an air-tight bulb. The plant uses the same water and air over and over again." Click to enlarge.

[Caption updated. Thanks! - Dave]

Looking closely at it, you can see water droplets on the inside. I think it's more of a tiny terrarium with a plant of some type inside, perhaps a fern?

She's holding a Crookes Radiometer, I believe, and the little vanes in the vacuum bottle are spinning like crazy because she's sitting under a skylight.

Could be a large wattage incandescent lamp - or perhaps a thermionic valve.

When I started work (over 40 years ago) designing electrical services for buildings etc I was picked up on Day 1 for using the word 'bulb' when I should have said 'lamp'. Bulbs grow in the ground; lamps are put in light fittings. So there!

[So this could be either, or both. - Dave]

Honestly, it looks like a tiny plant in a tiny vase to me. And the wooden base would make sense.

[The condensation on the glass would seem to support your hypothesis. - Dave]

There's no connector. Instead, there's a wooden base, which would not be advisable, given the heat a bulb that size would generate.

It's hard to see what's inside the bulb, but my guess is some kind of glass flower arrangement. That would explain the wooden base, so it could be set on a table.

It looks like some kind of an craft project, re-purposing large old light bulbs.

If you like this kind of thing get your incandescent bulbs soon. They are fast becoming a thing of the past.

But I'm more interested in what it is she's sitting on (appears to be a glass-topped table with no glass and no way to hold glass), and even more so by the rodent in a porkpie hat!

What's the big idea?