From the Gardner book:
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.
(Hint- The hollow earth)
Related thread: Gardner's book, A JOURNEY TO THE EARTH'S INTERIOR — Further Gardner Arctic material alongside the September 2019 Gardner posts