Hyphae and mycelium are structures found in fungi. Hyphae are thread-like filaments that penetrate into substrates and absorb nutrients. They secrete enzymes that break down nutrients into smaller molecules before being absorbed. When hyphae come together and fuse, they form a mycelium, which is a mass of branched, tubular filaments of fungi/08%3A_Protists_and_Fungi/8.09%3A_Fungi_Structure).

Here are some key points about hyphae and mycelium:

• Hyphae grow at the tip with the help of an organelle called the spitzenkörper.
• Sometimes hyphae create individual cells by forming walls called septa/08%3A_Protists_and_Fungi/8.09%3A_Fungi_Structure).
• New hyphae come from spores on the mycelia/08%3A_Protists_and_Fungi/8.09%3A_Fungi_Structure).
• Only dikaryotic (those with 2 nuclei) mycelium are capable of sexual reproduction while homokaryotic mycelium reproduce asexually.
• The hyphae of most fungi are divided into cells by internal walls called septa (septate hyphae), while the hyphae of some fungi are not separated by septa (coenocytic hyphae) /08%3A_Protists_and_Fungi/8.09%3A_Fungi_Structure).
• Mycelium is the vegetative part of the fungus and can be microscopic or visible as mushrooms, toadstools, puffballs, and truffles/08%3A_Protists_and_Fungi/8.09%3A_Fungi_Structure).
• Fungi can create networks with plant roots through their mycelium, creating a cross-kingdom web known as the underground network.
• Mycelium is an important food source for many soil invertebrates and is vital to agriculture and almost all species of plants, many species co-evolving with the fungi.

In summary, hyphae are thread-like filaments that penetrate into substrates and absorb nutrients, while mycelium is a mass of branched, tubular filaments of fungi formed by the fusion of hyphae. Mycelium is an important part of the fungus and can be microscopic or visible as mushrooms, toadstools, puffballs, and truffles.