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Peltigera membranacea cryofracture highlighting its tissue structure

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Peltigera membranacea  lichen thallus cryofracture highlighting the organization of distinct tissue layers within heteromerous lichens. At the top of the image is the ventral surface of the lichen showing the thick and loose hyphae of the medulla, and an absence of a lower cortex; a diagnostic character for the  Peltigera genus. The lower right corner of thge image shows the top surface of the epidermis layer covered in a waxy, hydrophobic coating. The dense layer between the epidermis and the emdulla is the photobiont layer, where colonies of tiny cyanobacterial Nostoc  photosymbionts reside within a gelatinous carbohydrate matrix. Tissue fixed in 1.5% glutaraldehyde in cacodylate buffer and osmium tetraoxide, dehydration series in ethanol, cryofractured in liquid nitrogen, critical-point dried, and sputter coated in gold about 320 atoms thick. Imaged using Quanta 250 scanning electron microscope, working distance 18.7 mm, secondary electron detector, accelerating volt...
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Devonian progymnosperm wood charcoal from Cottonwood Canyon, Wyoming

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Charcoal collected by Mihai Tomescu along the Souris river at Cottonwood Canyon, Wyoming, USA in 2017 showing diagnostic features typical of progymnosperm wood: clustered pits in the tracheids. Notice how the pits are closely clustered, and the tracheids are smooth between the pit clusters. This compression was collected from Devonian sediments roughly 400 million years old, give or take 20 million years. No chemical fixation. Sputter coated in gold about 320 atoms thick. Working distance 25.5 mm, backscatter electron detector, accelerating voltage 30 kV, spot size 4.0, scale bar 50 µm, magnification 1,250X, Quanta 250 electron microscope.
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Phytophthora cinnamomi germinating on a Port Orford Cedar leaf

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Leaf of Chamaecyparis lawsoniana, Port Orford cedar, baited with Phytophthora cinnamomi,  causal agent of 'phytophthora dieback', showing a clump of agar, emerging hyphae, and scattered bacteria. Leaf was sourced from HSU campus, and P. cinnamomi  was sourced from Chris Lee's personal culture collection, and incubated together in soil suspension for one week. Leaves were fixed in 1.5% glutaraldehyde in 50 µM cacodylate buffer and osmium tetraoxide, dehydrated in serial dilutions of 100% ethanol, and critical-point dried. Sputter coated in gold about 320 atoms thick. Imaged using Quanta 250 scanning electron microscope, working distance 13.9 mm, backscatter electron detector, 30 kV accelerating voltage, spot size 3.0, 300X magnification.
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