Sunday, February 06, 2005

Sensitive Fern and Hoarfrost

In area block D10, picked some fertile leaves (also called frondes) of the Sensitive Fern, [Onoclea sensibilis L.] that were sticking out of the snow. The ferns have either infertile or fertile leaves. Infertile would be like regular leaves of any plant, and the fertile leaves are like a seedpod but in this case bearing spores rather than seeds. Indeed this " fertile leaf" which looks more like a brown stick with a bunch of beads stuck to its branches in rows. It drops small brown specks, which can be seen when taped onto a sheet of white paper. I presume that these are spores.

This morning we have ice fog that leaves hoarfrost on all the trees. Looks like lacework among the branches, quite beautiful really. I imagine that this is caused by high humidity, and indeed it is currently at around 95% relative humidity outside, and the temperature well below the freezing mark which is now at –10 degrees Celsius or 14 Fahrenheit.
For an example of hoarfrost that is very similar to what we are looking at today see:

Reference: A Field Guide to the Ferns and Their Related Families of Northeastern and Central North America with a section on species also found in the British Isles and Western Europe by Boughton Cobb, Houghton Mifflin Company, Boston, 1963.
This is Number 10 in the Peterson Field Guide Series at the time of printing.

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