Vascular tissue allowed vascular plants to develop roots, which are organs that generally lie below ground. However, there are certain species that have aerial roots. Don't worry about it; there's always an exception in biology. These roots absorb water and nutrients for the plant; they also root it into the ground. So, they allow plants to grow taller because they provide stability to the above-ground portion of the organism. Vascular tissue also allowed for the development of leaves, which are an organ that is specialized for photosynthesis. And actually, we're going to see leaves come in two flavors. There are microphylls, which are small leaves supported by a single strand of vascular tissue. You can see an example of that here; we have a microphyll. In red, this is our vascular tissue. You can see that in this microphyll leaf, there's only this one strand of vascular tissue. Whereas megaphylls, which you can see an example of here, megaphylls, have a much more branched vascular system in the leaf. Of course, I've included a picture of a maple leaf there. You can see the vasculature going through the leaf. I'm not going to draw in all the little lines, but you can see it pretty distinctly in this leaf. This is an example of a megaphyll. And why did I pick a maple leaf? Because I love maple syrup.
Now, seedless vascular plants, again, show that transition from gametophyte dominant to sporophyte dominant life cycles. We've discussed alteration of generations before. All land plants show alteration of generations, and this is, again, just a life cycle in which both the diploid and haploid stages are multicellular. You have your gametophyte, which is that haploid multicellular stage of life that produces the gametes, and the sporophyte, which is the diploid multicellular stage of life responsible for producing spores via meiosis. Right? And a spore, again, is just an asexual, a unit of asexual reproduction. It's usually haploid and usually unicellular. Plants specifically evolved, what are called sporophylls, and of course, since these are modified leaves, this has to be vascular plants we're talking about. These sporophylls bear what are called sporangia, which are basically just enclosed structures in which spores are formed. You can see an example of sporangia here. All of these kind of reddish-brown dots on the backsides of these leaves are sporangia. This is actually a fern leaf. All of these are sporangia.
So let's actually turn the page and take a look at some other adaptations.