- The vegetative bodies of most fungi is usually hidden, being diffusely organized around and within the tissues of their food sources.
- The body of the fungi is composed of basic building units called hyphae which are minute threads of tubular walls surrounding the plasma membrane and cytoplasm.
- When combined, hyphae form an interwoven mat called mycelium the "feeding" network of a fungus.
- Hyphae are usually divided into cells by crosswalls called septa.
- Septa usually have pores large enough to allow ribosomes, mitochondria and even nuclei to flow from cell to cell.
- Fungi cell walls are made of chitin a nitrogen containing polysaccharide wall.
- Some Fungi are aseptate meaning their hyphae are not divided by septa. These type of fungi are called coenocytic fungi.
- Some fungi have haustoria which are modified hyphae that penetrate their host to absorb nutrients.