Though these look like leaves, they aren’t.  They’re liverwort, a plant related to moss that often grows right next to it.

The flat green ribbons place this plant in the thallose liverwort group.  There are also leafy liverworts that look like moss, some so tiny that they require an expert with a magnifying glass to identify them.

Liverworts (Marchantiophyta) are ancient plants with these amazing characteristics:

• They have no water transport system (i.e. non-vascular). Without internal pipes they’re at water’s mercy to come and go wherever it will. Thus they don’t grow tall.
• They have no protection against water loss so liverworts have evolved the ability to dehydrate and recover in a technique similar to hibernation.
• Liverworts’ cells contain only a single set of chromosomes (haploid). They produce diploid cells only for reproduction.  Animals and most plants are the opposite with double chromosomes in our normal cells and singles only for reproduction.
• Liverworts have no roots.  Instead they have specialized cells on the underside called rhizoids that cling to the surface.  Each cell is holding on!

Look closely and you can see that the “leaf” is a mosaic of plates, each with a dot in the middle.  The dots look like stomata for regulating water loss but they’re actually air pockets.  (Click here for a schematic from the University of British Columbia.)

Liverwort got its name during the Doctrine of Signatures era when people believed that plants that resembled a body part treated diseases of that body part.  Since liverwort resembled animal livers people thought it must be a good treatment for liver disease.  Liver + wort is “liver-plant.”   In reality, liverworts have no medicinal use.

Because they’re at water’s mercy look for liverworts in cool, damp, shady places.  I found these on a north-facing cliff near Breakneck Falls at McConnell’s Mill State Park.

(photos by Kate St. John)