Monday, October 31, 2016

Pulveroboletus ravenelii (Ravenel’s or Powdery Sulfur Bolete)

August-September, 2016. When I first spotted this mushroom, I was walking through a deeply shaded section in a mixed hardwood-pine woods. It stood out against its background.

It was a bright, ‘fluorescent’ yellow.

When I touched its stem, my fingers were covered with a yellow chalky substance. This bolete is covered with a bright yellow partial veil material when young; none remained on the cap of this specimen but it persisted on the stem.

The pore surface on young specimens was a bright yellow and bruised blue when damaged. The blue bruising observed with many boletes results when cells are damaged and a compound called boletol present in the cells is exposed to oxygen (oxidized) producing a color change from colorless to blue. (Interestingly, remnants of the veil are also visible at the margin of this cap.)

The pores on this bolete are relatively large - 2-3 pores/millimeter – round or angular in shape, and somewhat translucent in appearance.

In late September, I spotted a bolete with a duller yellow cap that had patches of orange. I thought it was a different species of bolete but, again when I touched it…

the yellow, chalky material, clearly visible in this photo, came off on my fingers. Immediately, I knew I had found an old specimen of Ravenel’s bolete.

The pore surface of this older specimen was a dark olive-gray that still bruised blue when damaged. 

During the period between late August and late September, I found Pulveroboletus ravenelii at three different locations along the trail between the beach and the fishing area. The combination of the bright yellow color and the presence of the yellow, chalky material were key characteristics in identifying this species. 

Pulveroboletus ravenelii is found in North and Central America, as well as in some Asian countries and Australia.

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