20.1: Fungi What is a fungus? The Characteristics of Fungi Fungi are eukaryotes, use spores to reproduce and are heterotrophs. Fungi need moist, warm places to grow Most are multicellular, yeasts are unicellular Hyphae: branching threadlike tubes that make up the bodies of multicellular fungi Fuzzy looking molds have loosely tangled hyphae. The stalk and cap of mushrooms are closely packed hyphae. Mycelium: a complex network of branching hyphae may serve to anchor the fungus, invade food sources, form reproductive structures Cell walls of must fungi contain a complex carbohydrate called chitin Cross walls called septa divide hyphae into individual cells that contain one or more nuclei Pores in the septa let cytoplasm, organelles and nutrients flow throughout the fungus