Friday fabulous clubmoss

This is a rather poor picture of a very young Selaginella sporophyte (~1.5 mm), the typical and familiar generation of this club moss.  A student has been investigating the use of various common materials for cultivating the haploid generation of free-sporing vascular plants (ferns, clubmosses, horsetails).  It turns out that fine grained terrarium sand sold in pet stores works rather well for this when wet with very dilute liquid fertilizer.  Selaginella has rather smallish and poorly differentiated cones bearing their sporangia at the tips of branches.  The spores come in two flavors, big and little, differing greatly in their ability to disperse and their number.  The big spores become female gametophytes and the little spores become males, which are little more than a sex organ that produces sperm.  This is the same as pollen.  The females stay largely within their spore living primarily on stored food.  The arrow points to the large spore within which resides the female gametophyte that got impregnated and gave rise to this little diploid offspring.  On the grain below the arrow a few little brownish flecks are the little spores that house males.  Some cobwebby rhizoids can be seen above the arrow, outgrows of the female for anchoring, absorbing, and even entrapping small spores so that little males grow in her vicinity.  This part of their life cycle is seldom noticed and when you take pictures with a regular camera through a microscope the depth of field can be rather shallow.