Now fungi morphology is going to be a little strange, let's say, compared to what we've seen thus far. Fungal bodies are mostly made of what are called hyphae. These long filaments that are actually made up of 1 or sometimes many cells, and are surrounded by a kind of tube-shaped cell wall that will enclose all of them in a filament. You can see a microscopic image of hypha here. They are these filamentous strands you see. And we can see an artist's rendition of a hypha here. Each of these blocks actually represents individual cells and essentially, while the cells are technically independent, they do have pores between each other. And, these blockages or these divides in the cells, I should say, because they're not actually blockages, they allow passage between the cells. These divides are called septa. So here, this is a septum. That's going to be the singular form of the word. And, it's worth noting that these fungal cells, right, these hyphae, have a chitinous cell wall, which is actually a modified beta-glucose polymer. You might remember that beta-glucose is what is used to make cellulose, interestingly enough. Here however, these subunits have been modified with an amino acid-like group. And essentially, it, this polymer acts as a tough cell wall for the fungal cells. And it's actually also present in insect shells interestingly enough. And that's why when bugs die, their shells hang around and don't decompose or anything. Because there's really not a lot that digests chitin. It's a very tough resilient material. That's why, you know, you can keep, for example, an insect shell from a dead insect from, you know, a really long time ago. And also why, fungi tend to be or tend to have these resilient hardy cell walls. Now hypha refers to an individual filament and we use the term hyphae to refer to multiple hypha, so that's the plural form. The entirety of a fungus's hyphae is called the mycelium. So that's essentially the mass of the fungus, which is made up of all these interwoven hyphae that is called mycelium. So you might hear those terms used interchangeably from time to time, but just know that mycelium is the totality of the hyphae of a fungus. Say that 5 times. Now fungi, actually perform, what's called extracellular digestion. And essentially what they do is they release enzymes and absorb the nutrients, that the enzymes will break down compounds releasing nutrients and these nutrients get absorbed through, the fungal hyphae. Now it's worth noting that might sound really strange, but humans technically also perform extracellular digestion. Right? We put food into our gastrointestinal tract, and we release enzymes from cells, around the GI tract that break down our food and then those cells absorb the nutrients, as the food gets broken down. The difference really is that, we're doing this inside of our bodies whereas fungi, don't always, fungi don't usually do it like that. They will actually, or secrete these enzymes into the environment, break down the stuff, and then absorb it. So, not as weird as it sounds, but still different than the way humans do it. Now some parasitic fungi actually have these, special, hyphae called haustoria. And again, singular here is going to be haustorium; all these Latin words, I know. So a haustorium, that's going to be the singular form, and you can see them here. These are all plant cells and these dark bits that you see inserted into the plant cells; those are the haustoria. And you can tell because the fungus has been stained, this darker stain. So this band you see, that's the fungus and these nubs it's inserting into the plant cells, those are the haustoria. And this is what parasitic fungi are going to do to extract nutrients from plant cells. Now, with that in mind, fungi actually, generally, are really helpful to plants. Okay? So sometimes they're parasitic, always some bad apples in the bunch. Right? But, fungi are actually essential to many land plants, and they actually form this symbiotic association of hyphae and roots of vascular plants, obviously, because vascular plants are the only plants that have roots, and, as opposed to rhizoids, you might recall from plants. Now, this association of roots and fungi can be seen here in white, that is the, fungal body and the, little brown bits are roots. Basically, what you're looking at is, someone kind of like pulled a plant, flipped it upside down and brushed some of the dirt off the roots, and that's what we're looking at here. Now, there are actually two ways that these mycorrhizae can form. And notice that term mycorrhizae, right? Rhizae, that's referring to roots. Myco is referring to fungi. So we have fungal roots, basically. Now as I said, they're essentially, 2 different versions of mycorrhizae. This actually gets a little more complicated, you know, as I hope you realize by now we have to simplify things a little bit just to make it manageable to talk about and to paint some broad strokes pictures. But essentially you can have ectomycorrhizae, which form on the outside of plant cells, the extracellular surfaces. They don't penetrate into plant cells. And you can see an example of this right here. We have the artist's rendition in purple. These purple stringy bits, those are the fungi. And you can see that while they don't actually penetrate the plant cells, they will penetrate into the root of the plant and grow around the cells. And here you can see an image, an image of the ectomycorrhizae around a root. So we are, all this stringy stuff is the fungal body forming around the root. But it can also go the other way. Arbuscular fungi, which are sometimes referred to as endomycorrhizal, right, endo meaning internal. So, arbuscular fungi will actually penetrate into the cells in the roots of plants. However, in both instances, this is a beneficial relationship to the plants. Just 2 different strategies. So the main relationship here is that the fungi help the plants get certain nutrients and help them obtain water, and in return, the fungi are provided with nutrients by the plants. So with that, let's conclude this video, and I'll see you guys next time.