Re: More on A.pellucida

I have found some more information in an article by Trivelli and Lincke
(1931):
Fraenkel and Pfeiffer showed photomicrographs of the Ap dots first in
1889 (according to Neuhauss). In 1890 van Heurck and 1893 Zettnow
succeeded also with use of the new Zeiss apo 1.6NA, as said before a
monobrome naphtalene immersion lens.
Zettnow was able to count dots to 52/10um. He used a filter of
cuppramonium solution and iodine (ie violet). The diatom was mounted in
mercury iodide, and as said before the 1.6NA lens was a monobrome
naphtalene immersion lens.

Neuhauss in 1907 was slightly contradictonary as he mentioned van
Heurck and Zettnow used the same lens, but a Realgar mounted slide and
blue light (violet would be absorbed by Realgar). I guess both will
work.

Watch this remark on van Heurck's images (Neuhauss p 264, translated):
van Heurck tried to resolve the striae (Langstreifung) and pores
(Querstreifung) (1886). However, he masked in many images along the
edge of the diatom. Therefore, it was impossible to differentiate the
'Querstreifung' from diffraction lines [that are optical artefacts from
the edge of the valve].

Neuhauss reproduced a truly magnificent image from Ap, made with 275nm
UV-light in 1907. As far as I can make out this image originate from
the Zeiss labs where the new UV monochromat was developed, a glycerin
immersion 1.25NA. If Keith contacts me I can send him a couple of
images from the page of this book so that everybody could see it on his
website, as I have no webspace to show it on.

René.

.

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