Photo by John Nelson Dr. John Nelson

Each week The Columbia Star features an explanation and picture of a mystery plant given by Dr. John Nelson, the curator of the USC Herbarium. To learn more about the Herbarium, call him at 777-8196. His department also offers free plant identification. www.herbarium.org There are two basic reasons why you should make and eat guacamole.

First, it tastes great. Guacamole, of course, comes from the avocado plant, which is native to warm tropical forests of the New World. Now avocados have received a lot of bad press, as food sources, since they contain a good deal of fat, which seems to be the bane of modern existence. As it turns out though the fat inside ripe avocados is largely unsaturated or “good” fat. True, there are calories, but for the amount of guacamole you eat, it tends to be a lot healthier than similar foods with lots of calories. Some people use ripe avocado to spread on toast, in place of butter or margarine. Besides, avocado is full of vitamins, especially E and C, as well as plenty of minerals. The flesh is also high in fiber. Avocado oil, available as a cosmetic, is great for your skin, too.

Answer to last week’s mystery plant Christmas fern, Polystichum acrostichoides Now making guacamole can be an act of creative genius. Guacamole purists (like me) use only some lime juice, salt and pepper (maybe a little hot sauce) for its preparation, whereas fancy versions frequently contain combinations of chopped onion, tomatoes, jalapeño, and coriander. Perhaps the greatest guacamole controversies concern its texture, really smooth, out of a blender, versus a little lumpy, just mashed with a fork.

The second reason for making your own guacamole is that you get a houseplant out of it. Growing an avocado plant from a seed is rather simple…and it is this seed that poses a bit of a mystery.

The seed is relatively massive, compared to the size of the fruit. (This is a common trait of many tropical trees.) The avocado fruit itself consists of three distinctive layers. The outermost layer is the bright, shiny skin (green, or brown, depending on the variety), then a thick, soft interior layer (the edible part), and finally a thin, brown shell which covers the seed. The seed consists of a humble embryo surrounded by two swollen, yellowish or tan “halves”, which are what we call the seed–leaves. These seed– leaves store energy for the tiny embryo during its early growth.

Wash off the seed, leaving the shell on, and place it, big–end down, in a jelly jar holding a little water. After a couple of weeks, a root will appear at the bottom as the seed slowly sprouts. Once the leaves start to expand, you can pot up the seed. And now you have a little bit of the tropics, right in your kitchen.