The feather bristle

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Hobbyst46
Posts: 4277
Joined: Mon Aug 21, 2017 9:02 pm

The feather bristle

#1 Post by Hobbyst46 » Fri Feb 08, 2019 9:21 pm

Hi All,

Pennisetum Setaceum Rubrum is a common perennial ornamental grass - sometimes invasive. It belongs in the Poaceae family. The flowers are arranged as spikelets grouped into spikes. (source: Wikipedia). The small greenish-purple leaves of the floret are very thin, so ready to be mounted on the slide.

I mounted some of them in PVA-Acetate-Copper (the latter two components are said to preserve the chlorophyll). A warning about this mixed mounting media: With time, I see some "crystallization" in the medium (possibly caused by the acetate+copper), so it is not really permanent.
The cell rims are amazingly wavy. Is it because these parts have dried up upon maturation or were they like this from the start?

The surface of the cells bears many small pointed bumps, making the spike rough to the touch.
Within the floret, there is a white-looking feather bristle.

I mounted the feathers mostly in NOA61 (photos taken at 25X). They should be permanent slide. Actually, the hairs are fairly transparent tubes. They are ~10 micrometers in diameter and several millimeters long. They are nicely birefringent. The main shaft of the feather carries tiny spikes.
Attachments
Pennisetum setaceum rubrum spike-2.jpg
Pennisetum setaceum rubrum spike-2.jpg (197.5 KiB) Viewed 2994 times
Pennisetum setaceum rubrum-3.jpg
Pennisetum setaceum rubrum-3.jpg (460.43 KiB) Viewed 2994 times
6.3X0.16 Plan BF-2.jpg
6.3X0.16 Plan BF-2.jpg (143.19 KiB) Viewed 2994 times
10X0.30 neofluar.jpg
10X0.30 neofluar.jpg (337.38 KiB) Viewed 2994 times
40X0.75 neofluar Ph2 + pol.jpg
40X0.75 neofluar Ph2 + pol.jpg (230.22 KiB) Viewed 2994 times
Last edited by Hobbyst46 on Fri Feb 08, 2019 9:28 pm, edited 2 times in total.

Hobbyst46
Posts: 4277
Joined: Mon Aug 21, 2017 9:02 pm

Re: The feather bristle

#2 Post by Hobbyst46 » Fri Feb 08, 2019 9:23 pm

(continued) The various views are obtained by rotation of the polarizer. Please ignore the foreign black "loop" and tiny air bubbles in the first photo.
Attachments
Feather 6.3X0.16 POL.jpg
Feather 6.3X0.16 POL.jpg (209.93 KiB) Viewed 2993 times
Plan 25X0.45+POL(1).jpg
Plan 25X0.45+POL(1).jpg (171.28 KiB) Viewed 2993 times
Plan 25X0.45+POL(2).jpg
Plan 25X0.45+POL(2).jpg (183.08 KiB) Viewed 2993 times
Plan 25X0.45+POL(3).jpg
Plan 25X0.45+POL(3).jpg (169.24 KiB) Viewed 2993 times
Plan 25X0.45+POL(4).jpg
Plan 25X0.45+POL(4).jpg (174.75 KiB) Viewed 2993 times

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mrsonchus
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Location: Cumbria, UK

Re: The feather bristle

#3 Post by mrsonchus » Sat Feb 09, 2019 12:42 am

Superbly interesting and beautiful images! I love trying to identify grasses as they're so difficult, involving for a definite ID close dissection of the spikelets and the number of tiny florets within each, often right down to the position of the stigmas atop the minute ovary!

Please post more if you have them, they're very interesting!

Great post, thanks, John B. :)

p.s. the 'wavy' cells walls are normal and not an artifact - many leaves have these wavy cell-walls of their epidermis, even some mosses.
John B

Hobbyst46
Posts: 4277
Joined: Mon Aug 21, 2017 9:02 pm

Re: The feather bristle

#4 Post by Hobbyst46 » Sat Feb 09, 2019 8:44 am

Many thanks John B.

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