The successful deployment of the Semantic Web of Things (SWoT) requires the adaptation of the Semantic Web principles and technologies to the constraints of the IoT domain, which is the challenging research direction we address here. In this context we promote distributed reasoning approaches in IoT systems by implementing a hybrid deployment of reasoning rules relying on the complementarity of Cloud and Fog computing. Our solution benefits from the complementarity between Cloud and Fog infrastructures. Indeed, remote powerful Cloud computation resources are essential to the deployment of scalable IoT applications, and locally distributed constrained Fog resources, close to data producers, enable low-latency decision making. Moreover, as IoT networks are open and evolutive, the computation should be dynamically distributed across Fog nodes according to the transformation of the network topology. For this purpose, we propose the Emergent Distributed Reasoning (EDR) approach, implementing a dynamic distributed deployment of reasoning rules in a Cloud-Fog IoT architecture. We elaborated mechanisms enabling the genericity and the dynamicity of EDR. We evaluated its scalability and applicability in a simulated smart factory use-case. The complementarity between Fog and Cloud in this context is assessed based on the experimentation conducted.