Epidermal tissue is kind of like the skin of the plant. It protects the plant from pathogens, physical damage, and also helps prevent water loss. Now, epidermal cells will actually secrete this waxy film called the cuticle that helps prevent water loss. And you can see in this image the water beading up on the surface of this plant because of the cuticle. It's hydrophobic and causes the water to bead up on the surface. It also prevents the water from leaving the inside of the plant. Sometimes on the epidermis of plants, we'll find what are called trichomes, little hair-like structures made of specialized epidermal cells, and they carry out a very wide range of functions. They can be involved in water loss, help defend against herbivores by containing some sort of nasty chemicals. Like, these are chemical trichomes here that are meant to prevent herbivores from eating the plant they cover. They can also help reflect sunlight and, in fact, they can even be involved in eating animals like we see here. This stalk of the plant is covered in these trichomes, which are the little hair-like things with the beads on the end. And you can see that these trichomes have wrapped around this hapless insect here, which is now destined to become plant food.

Ground tissue is the third type of tissue found in plants. So, we have epidermal tissue, vascular tissue, and ground tissue. Ground tissue is basically everything that isn't epidermis or vascular tissue. So it's kind of the grab bag, but generally speaking, ground tissue is going to be responsible for producing and storing important molecules for the plant. Generally, we can separate the ground tissue into two regions, the pith and the cortex. The pith is going to be this inner region here, and it is basically ground tissue that's surrounded by the vascular bundles. Now, what we are looking at, just to be crystal clear, is the cross-section of a plant stem right here. So, basically, if we had a plant stem, and, I don’t know, like here’s a little leaf coming off of it. You know, if we cut that across, and then took that piece and were to look at it, look down on that cross-section, that's what we're looking at right here. So that interior layer is the pith. You're going to find the cortex actually all the way out here, the layer marked 6, this kind of dark layer on the outside, that's the cortex. It's the ground tissue outside of the vascular bundles. So this whole region in here, those are the vascular bundles. This region marked 3 is the xylem. Oops. Spelling it the French way there. Put an extra e on the end. Kidding. And then 4 here, this is the phloem. And these are the vascular bundles. So the pith is the inside, 6, that's the cortex on the outside. And 7, what's labeled 7 here is actually our epidermis. So, the cortex can actually be broken down into certain layers itself. We have the endodermis, which is the innermost layer of the cortex. So it's going to, form the cell boundary between the cortex and the vascular tissue of the plant. On the other side, we have the pericycle, which is a thin layer of tissue between the endodermis and the phloem. So essentially, if we were to kind of zoom in on this image right here, we'd basically have the phloem, which is layer 4, and then we'd have the pericycle, and then the endodermis. And we're going deeper into the plant in this, as we go along this way.

Alright. Let’s flip the page and talk about some of the specialized cells of the ground tissue system.