Dr. Nansen was a Ph.D. in biology, and he collected samples first hand, then examined them through his microscope. He confirmed that they were pollen.
Here are some comments and quotes in this regard from Seven Days North of
Tibet-
http://www.holloworbs.com/Seven_Days.htm
On July 18th Doctor Nansen brings our attention to other polar anomalies
quite noticed and well documented by other explorers- at this point the ship
was just above 81* North.
Page 201: Wednesday, July 18th. "Went on an excursion with Blessing in the
forenoon to collect specimens of the brown snow and ice. ... The upper
surface of the floes is nearly everywhere a dirty, brown color, or, at
least, this sort of ice preponderates, while pure white floes ... are rare.
...; but the specimens I took today consist, for the most part, of mineral
dust mingled with diatoms and other ingredients of organic origin."
Dr. Nansen mentions in the footnotes that: "larger quantities of mud,
however, are also often to be found on the ice ... but are doubtlessly more
directly connected with land ."
Page 488: "Siberian driftwood, ... as well as the mud found on the ice ...
even when we were as far North as 86*."
The question always goes back to the manner in which one interprets such
data. The sediment types from the mud typically found on the ice floes
seemed to correspond to Siberian rivers, wherefrom some ice could have
broken off. But the sediment types also correspond to Alaskan sediments-
they did not correspond to European sediments. Driftwood found near
Greenland was definitely of Siberian and Alaskan origin, not European. A
Hollow Earther would conjecture that the mud types could correspond to a
land mass at the entrance to the hollow world. The problem is that we have
no sediment samples from such a place to compare with the mud from the
floes, but since the suspected entrance lies on the same side of the polar
basin as Siberia and Alaska, why wouldn't such a place provide a more likely
explanation for the mud found on the ice floes at that very point? Such a
place would be a closer source.
Granted that sediment types from the mud found on the icebergs do not
constitute absolute evidence of a hollow Earth. But what about the pollen
dust which covered huge expanses of ice? Such pollen coverage has been
documented from the Franz Josef Islands as well as over in Northern Canada.
There may have been land masses which could have accounted for the existence
of a bit of mud on the ice, but there was certainly nothing in the way of
vegetation which could have produced pollen which blew about and settled all
over the ice. Has any observer ever noticed huge clouds of pollen dust
traveling across the Northern parts of continents and the Artic Ocean in
order to deposit themselves on the ice up at 82* North? ( No! ) Again,
Nansen was not the only Arctic explorer to note pollen on the ice. Since
the ice has movement, such clouds of pollen would have to be typical and
usual in order to continally cover the ice. Would not a polar opening,
through which the winds of a continent are funneled, better account for such
an observation?
Sediments and pollen dust was not the only discolorations encountered on the
ice by the Fram and its crew. Clouds of volcanic dust were found, too,
consisting of iron and carbon particles. These huge clouds descended on the
Fram and settled everywhere and enveloped everything, causing discomfort and
irritation. Nansen noted: " Let us go home. What have we to stay for?
Nothing but dust, dust, dust. " There were no active volcanoes at this time,
certainly not for thousands of miles. A polar opening to the interior of our
planet, with an associated land mass, provides a plausible explanation.
From Marshall Gardner´s book, on pollen in the high Arctic:
"By August first he had reached a point near the Petowik glacier which
lies just northward of the "Crimson Cliffs" of Sir John Ross. This is
so called from the fact that on the snow clad cliffs and glacier
surfaces at this point Sir John Ross, in 1818, discovered a red
deposit which had fallen about and mixed with the snow, giving it a
reddish color which was pretty widely distributed. What was it? For a
long time this was a mystery, but it was at last proven to be of
vegetable origin: now, the point to be taken up in detail later is
simply this: where could any vegetable matter, either a pollen from
larger plants or a very humble sort of red mossy or spore like
growth, come from? There is no other case in the whole realm of
botany that would justify us in assuming that a plant can grow on ice
bergs or on snow. A plant requires certain elements and certain
temperatures. Evidently, somewhere those factors must be in
existence. Where, we shall see later."