appressorium

An appressorium is a specialized organ found in some parasitic fungi. It is the flattened, thickened tip of a hyphal branch that helps the fungus attach to and penetrate its host.1

When fungal spores land on a susceptible host, they can germinate and produce a germ tube. If this tube finds an opening, it enters the host. For some fungi, the germ tube develops an appressorium, which presses against the host's outer layer (epidermis) and punctures it, allowing the fungus to establish itself and grow. This process is crucial for parasitic fungi to obtain nourishment from living organisms, often causing disease.2