A plant attached to substrate may be attached to sand, soil, mud, rock, or a log.
Some attached stem plants can fragment. These fragments may be observed free-floating even though the plants are not actually truly free-floating plants.
This feature is most applicable if you can observe a plant in situ. You may also be able to infer a plant's attachment status when it is not in situ. For example, if your specimen has roots holding bits of soil, it is probably attached.
If you are not sure, skip this feature.