Apologies for the late entry again - I was at a conference this morning, and then had connection difficulties all afternoon and evening. Connor has put together this entry:
Today's Botany Photo of the Day exhibits a member of one of the lesser known groups of the vascular plants, the monilophytes. This particular species, Equisetum pratense, is commonly called meadow horsetail and has, like many horsetails, a very wide distribution.
The monilophytes and the seed plants (gymnosperms and angiosperms), make up a group known as the euphyllophytes. In A classification for extant ferns (PDF), Smith et al. depict the euphyllophytes as being a sister group to the other major vascular plant group, the lycophytes. This means that an early dichotomy gave rise to the lycophytes on the one hand and the seed plants and ferns on the other.
Within the monilophytes aka the ferns, Smith et al. have described four classes, taxonomy above which is still unclear and has been avoided. Included in the four classes is Equisetopsida with a single order and family, Equisetales and Equisetaceae. The lone genus is Equisetum with 15 species.
Despite of having only one of almost everything, the equisetophytes are numerous in the fossil record. Spenophyta: Fossil Record describes these unfortunate organisms, some of which reached 30 metres in height and possessed secondary growth.
Unlike the seed plants, Equisetum is homosporous, meaning they produce only one type of spore. The seed plants (PDF) produce two types of spores which develop into two types of unisexual gametophytes, pollen and (what later become seeds) ovules. Compared to the life cycle (PDF) of a horsetail which includes a free-living, bisexual (sometimes just male), and photosynthetic gametophyte, it is clear that a trend to gametophytically reduce has been present (courtesy of BIOL 210!).
Many thanks to xavierraynaudphoto@Flickr for today's photograph (original via the BPotD Flickr pool).
Daniel:
What does it mean when you state that some of the members of this family "possessed secondary growth"?
I would assume that secondary growth means an active vascular cambium that produces lateral growth, that is, an increase in girth. (eg. woody plant)
Jonathan - although no living equisetophyte has secondary growth (Equisetum giganteum gets remarkably tall despite this), some fossil plants appear to.
The horsetail does indeed have a wide distribution, including use in public art! Next summer, the Puget Sound area will enjoy the fist 15 mile long segment of a brand new Light Link Rail system that will run from Westlake Center in Seattle south to the SeaTac airport. As described on the Sound Transit web site "the tall green and black Safety Spires transform the Operations & Maintenance yard’s Overhead Contact System (OCS) poles into a celebration of transit, technology, and nature. One of the original inspirations for this artwork, created by artists Dan Corson and Norie Sato, was a prehistoric plant indigenous to this region – commonly known as the horsetail or Scouring Rush. The patterning on the horsetail, along with allusions to bamboo and spring growth seemed evocative of the renewal, maintenance and caring for the system taking place at the facility, the artists say." There is a small photo of the horsetail themed poles on the Sound Transit Public Art web page. http://www.soundtransit.org/x3908.xml
Long-time Seattle area residents will recall fondly the oversized "R" from the old Rainier brewery logo that looked down on the I-5 freeway just south of downtown. The very same "R" has been restored and reworked into public art as the first letter of the word "Rail" at the same O&M yard. Visitors stopping in Seattle on their way to the Winter Olympics in Vancouver in 2010 will be able to take Light Rail to and from the airport and skip the rental car or taxi ride. Light Rail Map at: http://www.soundtransit.org/x1171.xml
may i please say thank you to
the good people who write so
many interesting and informative
comments -i was not aware of
the rail and logos and all the who
whats and whens- my local florida
papers or web sites would have not
printed all the news aboutall your news
thank you all
I can totally see how this plant is beautiful ( like most plants) but personnally when I see this picture the only thing that comes to my mind is "good, it looks weak"!
Equisetum is a most unwelcomed guest in some areas around here.
I didn't know, though,that it was a "free-living, bisexual"! that does make it a bit more friendly, I must say!
Thank you very muh for choosing my picture. Cheers