Maybe the focus is too much on the bulb. Soil, after all, is not a static uniform medium, but a dynamic entity full of microorganism and insects that is actually moving around. When you flood a pot with a bulb in it the soil particles sort of float, until the excess moisture flows through the medium and starts flowing out of the holes of the pot, when the soil medium settles down again. So maybe the soil in a pot is moving up, as well as the bulb moving down. Calochortus, as Paige pointed out always end up at the bottom of the pot no matter what. They are true bulbs and the bulb you see is the bulb you saw last year - sort of. Of course it has added mass, and, yes, I agree, it can grow downwards, but they also have thick roots that look like retractile roots when they are in full growth before flowering. It's too simplistic to think of a bulb as a globular object on a string that is being pulled through a dense uniform medium. The medium must play a role - after all we all know that rocks move up through soil and there isn't anything pulling or pushing them! Diana Telos