Hyphae
The microscopic filaments that branch and interconnect to form the body of a fungus.
Hyphae (singular: hypha) are the microscopic, branching filaments that constitute the body of a fungus. Each hypha is a tubular cell that grows from its tip, extending into substrate as new cell wall is laid down behind the growing front.
A single hypha can extend for centimeters and produce countless side branches. The collective network of hyphae forms the mycelium — the vegetative body of the organism.
Hyphae are unusual cells. Unlike most animal and plant cells, they grow primarily in one direction. They secrete extracellular enzymes that digest organic material outside the cell, then absorb the resulting small molecules across the cell wall. This external-digestion strategy is part of what makes fungi such effective decomposers across nearly every terrestrial ecosystem.