A good question came up this morning during our Tuesday Morning Walk: what is the difference between clubmosses and true mosses? I shall try to answer this question as simply as possible without getting bogged down in botanical jargon.
Mosses are very primitive plants. They have no vascular system, meaning they have no stem, no way to support themselves, and no way to transport water and nutrients internally (phloem and xylem). Therefore, they are typically very small plants, living close to the ground where they can spread out and use the ground as support.
Here we have an example of a sphagnum moss, Sphagnum papillosum.
When you look at a moss, the green leafy bit, you are looking at the part called the “gametophyte.” When the gametophytes mature, they produce sporophytes, a result of sexual reproduction. In other words, the gametophytes produce eggs and sperm.
The moss we saw today was a Polytrichum, or hairy-cap moss. The common name, hairy-cap moss, come from the fact that the tips of the sporophytes have hairy caps, see below:
In the case of Polytrichum, the male reproductive parts are on one colony (the ones with the splash cups – see photo below), the females on another (they just look like green moss – no overt structures). Rain splashes the sperm from the male splash cup and they swim outwards across the wet plants in search of eggs on the female plants. When fertilization occurs, the sporophyte is produced (see above). This structure releases spores when it matures, which explode out onto the landscape in hopes of starting new colonies.
Clubmosses, on the other hand, are fully vascularized plants. They have stems, roots, etc. – all the supporting structures that every other vascular plant (raspberries, cattails, oak trees, etc.) has, including phloem and xylem. Remember, true mosses lack these transport systems and must therefore wick moisture along their leaves. Note that the clubmoss below, Huperzia lucidula, commonly called shining clubmoss, stands tall and erect, thanks to its stem.
Here’s another shot of the same plant, with my toes for scale. As you can see, it is much larger than (most) true mosses.
Like true mosses, however, clubmosses have sporophytes and gametophytes, and reproduce via spores. The tall yellowish structures you see in these photos are the sporophytes, and when I tapped them with my foot, clouds of spores, like smoke, drifted away (very difficult to photograph).
So there you are, in a nutshell, the very basic differences between true mosses and clubmosses.