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Posts tagged “Onoclea sensibilis

Wild Turkeys Dine on Sensitive Fern Spores

1-22-18 wild turkey IMG_0600Wild Turkeys usually forage in flocks as they search the ground for food. Acorns, hickory nuts, beechnuts, ironwood and white ash seeds, hawthorn and witch hazel fruits make up a lot of their diet in fall, winter and spring. In the summer, seeds of grasses and sedges as well as invertebrates are eaten. In winter, when snow has accumulated, leaves of sedges, evergreen ferns, hemlock buds, burdock seeds and spore-covered fronds of sensitive ferns tend to be more accessible and readily eaten.

The fertile fronds of sensitive fern (Onoclea sensibilis) persist all winter, sticking up out of the snow as if beckoning to hungry turkeys. Upon finding a clump of these fertile fronds, a turkey will peck repeatedly at them, causing the sori (clusters of sporangia which produce and contain spores) to burst and release thousands of spores onto the surface of the snow.

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Fertile Fern Frond Spores Dispersing

 

6-23-16  FERTILE FRONDS - royal, interrupted, cinnamon, sensitiveFerns differ from flowering plants in that they reproduce via spores, not seeds. The spores are borne on what are called fertile fronds (leaves).  Ferns have two kinds of fronds, fertile and sterile. Sterile fronds lack spores, are green, and do most of the photosynthesizing.

The fertile part of a fern can be very similar to, or totally unlike, the sterile part, depending on the genus or species.  Some ferns have sori (tiny clusters of sporangia, which contain the spores), commonly referred to as “fruit dots,” on the back of the blade of their fertile fronds.  Wood ferns have this arrangement, and the two types of fronds (fertile and sterile) are so similar it’s hard to tell the fertile (spore-bearing) from the sterile fronds without looking at the backs of the fronds. Others, such as Christmas Ferns, bear their sori on just a portion of the frond (tips).  And still others, such as some of those pictured, have fertile fronds that are completely separate from the sterile fronds.

When the difference between the fertile and sterile fronds is noticeable, the plant is called “dimorphic”. In some ferns this dimorphism is extreme.  Cinnamon, Royal and Sensitive Ferns all have separate fertile fronds that are not green and only bear sporangia.  Interrupted Fern spores are borne in sporangia that appear in the middle of stalks that also bear green pinnae.  The spores of all of these species of ferns are currently maturing and dispersing, which can be observed by lightly tapping a fertile frond.

(The next Naturally Curious post will appear on Thursday, June 23rd .)

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