Silica deposit location
This is a transverse section through the stem of a Horse Hair (Equisetum arvense.) This is the epidermis of the middle layer in the internode region of the stem, e.g., www.flickr.com/photos/14643312@N02/17227273543. The image is with partially crossed polarizers. The silicate deposition which is birefringent (bright white here) appears to be on the inside of the epidermal cell walls consistent with what is reported. Specimen collected along the Dowagiac River, 25 May 2015. In retrospect, the stem was not perfectly straight in the paraffin block and it was too thin.
The protocol was as follows. Specimens fixed in FAA (formaldehyde, acetic acid, ethanol) 48 hr. Dehydrated in IPA at 35, 50, 70, 85, 91, 95, 99 %. Infiltrated with paraplast saturated xylene 48 hr followed by 3 Paraplast baths prior to embedding in Paraplast. Sectioned 7 um thick on a Spencer 820 microtome. Cleared in xylene, 5 min, 2X. Rehydrated in 99, 95, 80, 70 %IPA. Stained in Johansen's Safranin-O, Fast Green (24 hours in Safranin-O, 15 sec. in fast green). Cleared 2 X in xylene 10 min each and mounted with DPEX.
Photographed in polarized light on a Spencer 42 petrographic microscope at original magnification of 1000X using a Sony NEX-5N and a Leica MIKAS 1/3X adapter. This is a dry image with the aperture of the Zeiss 100X objective reduced to match the NA=1 of the polarizing condenser.
Silica deposit location
This is a transverse section through the stem of a Horse Hair (Equisetum arvense.) This is the epidermis of the middle layer in the internode region of the stem, e.g., www.flickr.com/photos/14643312@N02/17227273543. The image is with partially crossed polarizers. The silicate deposition which is birefringent (bright white here) appears to be on the inside of the epidermal cell walls consistent with what is reported. Specimen collected along the Dowagiac River, 25 May 2015. In retrospect, the stem was not perfectly straight in the paraffin block and it was too thin.
The protocol was as follows. Specimens fixed in FAA (formaldehyde, acetic acid, ethanol) 48 hr. Dehydrated in IPA at 35, 50, 70, 85, 91, 95, 99 %. Infiltrated with paraplast saturated xylene 48 hr followed by 3 Paraplast baths prior to embedding in Paraplast. Sectioned 7 um thick on a Spencer 820 microtome. Cleared in xylene, 5 min, 2X. Rehydrated in 99, 95, 80, 70 %IPA. Stained in Johansen's Safranin-O, Fast Green (24 hours in Safranin-O, 15 sec. in fast green). Cleared 2 X in xylene 10 min each and mounted with DPEX.
Photographed in polarized light on a Spencer 42 petrographic microscope at original magnification of 1000X using a Sony NEX-5N and a Leica MIKAS 1/3X adapter. This is a dry image with the aperture of the Zeiss 100X objective reduced to match the NA=1 of the polarizing condenser.