We’ve taken an in-depth look at the lines of evidence Margulis developed to test her hypothesis, using mitochondria as an example. But, of course, Margulis had proposed that it wasn’t just mitochondria that had evolved from endosymbionts; she thought that plastids and tubule organelles had evolved from endosymbionts too. In the same article where she reported all the evidence she’d gathered about mitochondria, she also explained the evidence relevant to these other organelles. Plastids, at least, did even better than mitochondria. You can see on the chart below that every test result supported the idea that plastids evolved via endosymbiosis.
The tubule organelles, however, didn’t fare as well. They are passed to offspring in some cases and there didn’t seem to be any organisms that contained precursors to these structures, but most of the tests were inconclusive or simply hadn’t been done yet. Margulis still thought they had evolved via endosymbiosis, but the evidence supporting this view wasn’t very strong.