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Sporangia

Lady Fern Spores Maturing

Ferns are non-flowering plants which reproduce by spores, not seeds, and have a vascular system that transports fluids (unlike mosses, algae and liverworts).  Spores are typically located inside a capsule, or sporangium.  In many species of ferns, clusters of sporangia, called sori, are borne on the underside or margins of their fronds.  Often an indusium, or protective flap of tissue, covers each sorus, protecting the developing sporangia.  If you like to be able to give a fern a name, you will find that the shapes and arrangement of sori are a valuable identification tool.

Northern Lady Fern, Athyrium filix-femina, is a fairly common fern found in moist woods, swamps, thickets and fields.  It appears quite lacy and often grows in a somewhat circular cluster.  There are two distinguishing characteristics which are particularly helpful in recognizing Lady Fern.  One is its eyebrow-shaped sori.  If you look on the underside of a spore-bearing frond you will find that each sori is slighted curved, or arched, like an eyebrow.  The other diagnostic feature is the scattered thin, dark brown scales that are found on the stipe – the section of the fern’s stem between the ground and where the leafy frond begins.

This time of year, when the spores of many fern species are maturing, is a good time to learn the different ferns in the Northeast.  There are many excellent field guides to ferns.  One that you can easily tuck into your pocket is Lynne Levine’s Identifying Ferns the Easy Way.

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Horsetails & Scouring Rushes

5-20-16  equisetum044Horsetails and Scouring Rushes are in a primitive genus (Equisetum) of non-flowering plants.  Most of their stems are hollow and have distinct nodes, or swollen areas, where branches are sometimes attached.  Both stems and branches have vertical ridges and grooves.  Silica, embedded in the ridge tissue, led to the stems being used to scour pans as well as an abrasive for burnishing brass and finishing violins.

Equisetum leaves are barely recognizable as leaves – these pointed structures fuse into small sheaths surrounding each node.  A spore-bearing cone forms at the tip of the fertile stems.  If you look closely you will see that hexagonal plates (modified leaves) cover the surface of the cone.  Underneath these plates are the sporangia, in which spores are produced.  Upon maturation of the cone, the sporangia expand, split open and release their spores. (photo: Variegated Scouring Rush,Equisetum variegatum )

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Common Polypody Spores Dispersing

10-27-15 rock polypody 057Common polypody (Polypodium virginianum), also called Rock Cap Fern, is a perennial plant found most often growing on rock surfaces usually in moist, shady woods. Being a fern, Common Polypody reproduces by spores. Structures that produce and contain spores (sporangia) are found on the undersides of the fertile frond leaflets. The sporangia form round clusters called sori. The sori of Common Polypody are orange-brown when mature and lack the protective covering (indusium) that some other fern species have. At this time of year, the mature spores are being dispersed by the wind.

The ability of Common Polypody to tolerate extreme desiccation (the leaves roll up when moisture isn’t as available, and resume their normal state when moist conditions return) means it is well adapted to the extreme moisture fluctuations of rock surfaces. Its evergreen fronds are consumed in the winter by Ruffed Grouse, Wild Turkey, and White-tailed Deer.

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