pollen-squall at st vincents rock bristol

November 2023

Key to the observation of pollen as a tool to identify 'Squall at St. Vincent's Rock, Bristol' is the period when 'The rising squall, hot wells, from St. Vincent's rock, Bristol' was in Tasmania with Rev. Dr. Francis Russell Nixon, Bishop of Tasmania from 1842 to 1862. Turner's work, 'The rising squall, hot wells, from St. Vincent's rock, Bristol' was present in and around the Hobart Town area for nearly twenty years. It will almost certainly retain traces of pollen from species that were abundant in that area at the time but not present in and around London. The approach is twofold:

• To find pollen on the picture and try to identify the species.
• To identify species that were present in Hobart Town and its environs during the relevant period and determine whether this pollen is present on the picture.

Collection Methods

• Dry scrape of stretcher surface
  I scraped the surface with a dental tool and placed some sample directly onto a slide and some into a test tube. Some canvas fibres were included in scrapes close to the outer edges.
  Pollen was minimal in the direct to slide sample. If it was present it was possibly attached firmly to larger pieces of opaque material.
  Test tube samples are dealt with below.
• Dry collection of dirt and dust between stretcher and canvas.
  Pulled out with tweezers and placed into collection bags. Small parts were transferred dry to slides and this method collected a few grains of pollen tentitively identified as Polygonum.
  Some samples were transferred to test tubes for washing; these are dealt with below.
• Dry and wet stroking with cotton buds.
  If the cotton buds collected any pollen it was not evident when the buds were shaken or smeared onto slides.
• Tapings using clear one sided sticky tape.
  I cut small strips of tape and held one end with fingers whilst pressing the other (sticky) end onto the sampling location. Just one or two applications. I was therefore sampling an area of about 5mm x 5mm. The sampled end of the strip was stuck down to the slide and the finger held end cut off with scissors.
  Although this method made slides difficult to inspect due to bubbles in the adhesive, shiny tape surface and overlapping particles in the sample (there was no way to move or agitate the sample to redistribute particles on the slide) it did provide a sample that contained pollen.

Difficulties and Contamination

• Inclusions and defects in the slides were present on the three different brands that I used.
• Depth of field issues made it difficult to identify surface patterns.
• Age of the pollen caused deterioration, spherical pollen clearly had not dried evenly so there were many distorted specimens.
• Camera issues prevented really clear photographs.
• Lighting issues prevented accurate determination of morphology.
  I spent a lot of time and effort trying to top-light the slides and produced a prototype light ring which clipped to the objective. However, the bright white LEDs that I used did not produce the expected result. Camera response and LED spectrum were incompatible and even direct optical observation produced no enhancement.
• Finding databases of pollen specimens for identification. Australia is well served by APSA. OREME is good but I cannot make the location filter work.

Test Tube Samples

A number of papers suggested washing with alcohol and rehydrating with glycol solution. This could not be done with tapings. The other dry samples were successively washed, centrifuged, rinsed, some put in glycol solutions (which could not be dried), some just in water (heated and unheated) rinsed in acetone and dried. Centrifuging was carried out at each stage. Some pollen was detected but it was minimal.

Taped Samples

I now concentrate on making taped samples. November 2023.

The taped samples were found to be the best method of collection. Tapes could be applied specifically to small areas such as the canvas underneath the repair.

APSA catalogue entry for Dianella Tasmanica

The illustrated specimen was collected from Mount Franklin some 700km north of Hobart.

In Hooker's 'Flora Tasmaniae' of 1860 he wrote "Much the largest Tasmanian species' thus indicating that it was present in Tasmania around 1860.