A miniature forest of pale straws has taken over the near lake portion of my Dollar Lake property. Although rising several inches above the grass they are not obvious except in the low rays of the morning sun. It is appropriate that they are at their visual best in the “Dawn Time” because these plants, called Horsetails, are literally from the Dawn Times of earth history.
Although they may be small now, Horsetails come from a giant past. Perhaps the term “living fossil” is often overused (especially in reference to ancient aunts or family patriarchs) but these plants have been around for at least 300 million years and certainly qualify. In comparison, the dinosaurs are newbies and wannabes – having appeared and flamed out as the horsetails stood by and watched with unblinking stares.
The first members of this group attained tree stature at a time before trees were even a twinkle in evolution’s eye during the Carboniferous Period. These swamp plants shaded the first amphibians and provided perches for giant dragonflies. One early type, called Calamites, grew well over 60 feet in height on hefty trunks nearly two feet in diameter. Fossil imprints, such as the one I am holding in the photo below) record a plant that, except in scale, is identical with its modern descendants.
There are many different species of horsetail and all share “horstaily “features such as jointed ribbed stems and spore reproduction (none of this new-fangled flowering stuff). The plants grow via underground rhizomes which send up two different types of stems – fertile and non-fertile. And you thought I was going to say big ones and little ones, didn’t you!
Non-fertile stems are green and most produce whorls of strappy leaves (which just happen to make them look like horsetails, by the way). A detailed look at these stems will reveal rows of white silcates which give it a tough exterior and creates an abrasive quality useful for scouring out pots and pans (thus the common pioneer name of scouring rush).
Technically, it may be best to call my ancient little plants by their formal name of Equisetum arvense but let’s be civil about it and stick to Field Horsetail. My miniature crop consisted of early spring fertile stems only. These shoots are ghostly pale due to their lack of chlorophyll. Their only function is to produce a spore-bearing cone and then wither away. They rarely last more than a week.
The cones, or strobiles if you prefer-bile, themselves are made up of multiple scales which look like up-side down flowers – complete with petals. Tiny spores are produced by this structure and they drift off with each passing wind gust.
I teased several of my horsetails into releasing spore clouds and counted as many spores as I could. I reached 125 before….well, actually, no I didn’t. That was a shameless lie just to keep your attention long enough to tell you that you can’t see the individual spores with the naked eye. Under the magnification of a high power lens or scanning microscope, however, they take on a very interesting form.
Each spore is tightly wrapped with four elaters or tendrils upon release. Moisture sensitive, they un-furl like springs which aide in the spore’s motion. The enlarged foot pads at the end of each tendril give the whole thing a strangely alien appearance. One thinks of those alien invaders from “War of the Worlds.”
These horsetail spores are, of course, the exact opposite of alien forms because they have been an original part of our planet’s life for a very very – did I say very? – long time. We are alien forms by comparison.