|Galanthus 'S. Arnott' bulbs with elongated stems to adjust their position in the soil.|
As a snowdrop (in this case) clump develops, a mass of superimposed bulbs is formed, some of which, at the lower edge of the clump, or packed in the middle, may need to 'escape' to a more suitable depth. Unfortunately the clumps were already broken up by the time I looked for examples, so I can't illustrate this. Also, sometimes bulbs become buried too deep by mechanical means, and must also readjust their position in the soil.
No doubt this process is well-known to plant morphologists, but it has been fun to dissect some bulbs and deduce the situation for myself. Now I must attempt some controlled experiments to study the process as it happens.