The hyphal wall protects the pressurized cell against lysis, physical abrasion, chemical damage, and probably from other microorganisms and predatory invertebrates. Against these assets we can hypothesize costs for a cell that are associated with a wall. For example, phagocytosis is impossible, and the release of secreted molecules is complicated by the diffusional challenge presented by the mesh of microfibrils and interleaving wall polymers. A more controversial idea is that once delimited by a tough integument, growth becomes dependent upon the exertion of internal force to cause wall yielding, and most mycologists have posited turgor pressure as the origin of this force. In relation to growth then, it seems logical to suggest that fungal walls evolved to meet a multitude of needs, and that once a cell became walled, osmosis would automatically generate the turgor it required for growth.