Answer:
Schleiden had even supposed the nucleus to be a constituent part of the wall, sometimes lying enclosed between two layers of its substance, and Schwann quoted this view with seeming approval. Schwann believed, however, that in the mature cell the nucleus ceased to be functional and disappeared.
One way is that Igneous rock could erode and become sediment and deposited and slowly change into sedimentary rock, then get pushed down deep into the crust and changed by heat and pressure into metamorphic rock.
