Field of Science

Growing some haploid ferns

Today's task is to have students start growing some haploid ferns.  Your familiar ferns are diploids and they are asexual producing spores.  Novices often think they have spores but really they have sporangia, which have 128, 256, or 512 spores, there abouts, in them.  They are looking for something small, but they don't realize how small.  If you want to do this yourselves, here's how.  Find a fern with mature sporangia.  The sori, clusters of sporangia, usually look brown at this stage. Take two pieces of white paper.  Fold one into corners and crease it, then flatten the paper back out.  Place the fern frond on the paper sporangia side down.  Cover with the other piece of paper and leave it over night.  As the specimen dries out, the spores are shed onto the paper; look for brownish dust.  The creases make it easy to gather the spores by tapping the paper.  Go to a local garden store and buy a Jiffy 7; they cost about 15 cents.  It's a little compressed pellet of peaty soil in a little mesh bag.  Soak it in water overnight and it will expand.  Get a wide mouth pint canning jar, or an empty peanut butter jar, or something similar.  Turn it upside down and place the Jiffy 7, now more like a Jiffy 42 on the lid to produce a growth chamber terrarium.  Tap spores sparsely onto the surface of the Jiffy 7.  Cover with the jar, screw into the lid and place in a north window.  You don't want direct sunlight, so you also could place it back a ways from a brighter window.  A couple of weeks later you should see green growth.  It's OK to take them out to examine them, and should they need a bit of water place the Jiffy 7 in some shallow water for a few minutes, then return it to its growth chamber.  In 2 months you should have flat haploid ferns about the size of your little finger nail; they are actually called a gametophyte thallus, but it's still a fern, just haploid.  This is the sexual stage of the fern.  A mist of water will cause mature antheridia to release sperm and should a mature egg be around, fertilization will occur and a bit later you'll see the first frond of a diploid fern appear (the familiar phase).  With some patience this can will grow to maturity. 

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