A student brought in some Sargassum, it should still be in a bag in the window, but it might have rotted. I offer bonus points to students who bring in seaweed; the oriental market on Texas has seaweed cakes, rolls, crackers, etc. to bring in, and I encourage the students to taste them. Point out that because these algae store their photosynthates as something other than the sugar and starch we're accustomed to with plants, their 'sweet' flavor is different. There is a large bag of brown kelp on the shelves. I have the students touch it and feel how it is still 'damp' and jelly-like after all these years. This is an adapatation to keep them from drying out when they're exposed to air. Land plants have a waxy cuticle, but brown algae have evolved the agar that is so hydrophillic that they can last for weeks out of the water...and stay 'damp' for years. If you have students interested in genetic engineering, you might discuss the ability to move the gene for the production of agar into a green plant to make it drought resistant...Agar absorbs and holds water very well! One gram of agar in 100 ml of water makes a very stiff, bouncy gel. This makes it EXCELLENT for use in diapers, etc. because they can absorb far more than their volume in water...this is part of how 'leak free' diapers are made. If the TA works in a lab, bring in a plate of media (agar) or a gel (agarose, and no Ethidium Bromide)...I generally let the students play with it, poke it, bounce it off the table, etc. It's amazing how only a little powder can make it so solid. A good comparison is Jello.
A final sample is some Corallina in a small jar. Point out the jointed and very delicate appearance...the red algae and brown algae are very highly evolved, as much so as 'true' plants. I often tell students that if all green plants were to die tomorrow, we'd have either brown or red 'plants' on land in a million years or so!!! The red algae have an odd life cycle...this is how I explain it.
I start off with the tetrasporophyte. Because there is sporic meiosis, the sporophyte produces haploid spores. So far, same old song and dance. Some grow into haploid female gametophytes, some grown into haploid male gametophytes. Same old same old. The males produce sperm, the female makes an egg, and NOW things get different.
The sperm DO NOT have flagella. Notice how far down the evolutionary path these branched off....they PREDATE the development of flagella!!! So the sperm have to reach the egg simply by bumping into it. This means the males must produce a LOT of sperm. The egg also has to be VERY catchable, and it creates a structure called a trichogyne. This works like flypaper....and the sperm are the flies. There is a picture of this in the Atlas, page 48, 4.49. Very few eggs get fertilized...but it helps.
When a zygote DOES get formed, in a 'normal' organism, it would create ONE adult sporophyte. The red algae don't do this, because, well, they don't get many zygotes. So instead, when a zygote DOES get created and a diploid organism is formed, the zygote gets 'xerox copies' made!!!! These slightly modified copies of the zygote (they're elongated, not rounded) are called carpospores and are released from the carposporophyte. A sporophyte is what a zygote grows into....this is just the first sporophyte.
Now that multiple copies of the zygote have been made from the initial fertilization, they are released, and grow into the second sporophyte, the tetrasporophyte....and it starts all over again. It's like a dance, with an extra step thrown in with the carposporophyte generation. If the original zygote was released to grow into the tetrasporophyte, there would be so few tetrasporophytes that these things wouldn't be able to reproduce! So it creates a new adult plant, the carposporophyte, and uses it as a xerox machine to copy the zygote.