Sunday, October 26, 2014

Fern Sori

If you've followed my blog for long, you know I'm fascinated by ferns.  They're a group of plants that reproduce by spores, not seeds, and therefore have a very different life cycle.  And the spores are clumped in 'sori', usually on the back of the fern fronds, in patterns that vary by species.  These are easiest to see at this time of year.

These are the bright yellow sori of the Polypody Fern, a small fern about 10" tall usually, most often found growing in mats on the top of limestone boulders.  In this species, the spore dots (or fruitdots) appear only on the upper 2-3 inches of the frond, so that's all you're seeing here.

This is the pattern of the Male Fern.  In this and all of the remaining pictures, all you're looking at is the back of a single leaflet that I picked off the fern, and put down upside down to photograph.

Each 'sorus' or clump of spore cases ('sporangia'), contains microscopic spores, which provide for the fern's reproduction.  On the Male Fern they tend to be dark by this time of year, and very obvious.

This leaflet is from a Marginal Wood Fern, and the name comes from the fact that all the sori are found right along the margins of the sub-leaflets.  This species loves the limestone talus slopes below our Niagara Escarpment.

And this is a Woodfern leaflet.  Note the position of the sori on the sub-leaflets is similar to Male Fern, but the sori are lighter in colour and not as obvious.  And the sub-leaflets themselves are cut into deep teeth along the edge.

This is one of the most beautiful ferns, the Maidenhair Fern.  It's leaf doesn't look like a typical fern at all, the leaflets like this one being held in a circular pattern.

The sori are different too, forming lines along one side of each sub-leaflet that than dots.

And these are the sori of the Lady Fern.  They are larger and typically curved as here, making the back of the leaflets look quite dark.

Finally, this is the fertile frond of a Sensitive Fern.  This species grows an entirely separate frond with the sori or spore cases on it, in these tiny round balls, which by this time of year would be brown and dry.  They'll stand up above the snow right through the winter.

It occurs to me now that I've collected these photos that they'd be much more effective if they were paired with pictures of the entire fern fronds; maybe I'll do that someday.  In the meantime, I remain fascinated with ferns.  All these pictures except the last were taken in our yard, where I have a small fern garden along the old stone fencerow.

P.S.  To answer a question from Alain on the last post, also on ferns, here are pictures of the Green Spleenwort and the Maidenhair Spleenwort.  I haven't found a noticeable difference in size, but the first clearly has a green stem, while the second has a dark, brownish or purplish stem.

Green Spleenwort 

Maidenhair Spleenwort

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  1. I follow your blog all the time and find it very informative. Ferns are too often overlooked and they are interesting plants.

  2. Thanks for the botany lesson. I'm sure I used to know more about ferns when I was at school but wouldn't have been able to recall much of it - until now! They are much more plentiful in the wetter west of the UK than around here.

  3. Intriguing post. I had no idea about all these differences on ferns. I always thought that these markings were simply spores.

  4. Those are amazing photographs and that's a really interesting and informative post. The trouble with ferns is that they remind me of a really awful joke; and we get a lot of ferns round our part of the world.

  5. So interesting to see all those spores on the fern leaves. Thanks for sharing your interest.

  6. I think you are ahead of me on recognizing sori. I don't seem to find much variety in the ferns here

  7. Very pretty ferns and I like the mosses too.

  8. Amazing photos - yes, I'd like to see the whole fern sometime too. Your information is wonderful - I am going to look for more varieties when we are out and about.

  9. Ferns surely are ineresting plants - also attractive!

  10. Very pretty. I need to take a closer look at ferns.