18 THE MYCETOZOA:
populina. On lichened trunks of living poplars, the Rev.
William Cran has found in Aberdeenshire small forms of
Margarita metallica and Dianema corticatum, besides other
species.
Arboreal Mycetozoa.—Before leaving the subject of living
trees as a haunt for Mycetozoa, I should like to draw particular
attention to this " arboreal habitat " (as it may be called)
as one of which we have still much to learn. Two observers
only, that I know of, have systematically examined the
trunks of living trees with much success—the Rev. William
Cran, in Aberdeenshire, and Mr. Kumagusu Minakata, in
Japan. Both gentlemen are blessed with exceptionally
keen eyesight. I have had the privilege of being shown
some of his hunting grounds by Mr. Cran. Instead of
the sheltered woodland one is accustomed to regard as the
favoured haunt of Mycetozoa, I was taken to a bare
open country, divided into pasture and cornland by rough
granite walls, with here and there scattered homesteads, sheltered
from the weather by groups of trees. It was on these trees, as
well as on others even more exposed, that Mr. Cran pointed out
wonderful growths of Orcadella operculata, and scattered patches
of Badhamia affinis, B. versicolor, and Diderma arboreum, species
. which I had never seen growing before, nestling amongst moss
and lichens, at a height of five feet and more from the ground.
Many of the rare arboreal species, which have hitherto been found
in Scotland by Mr. Cran alone (for I saw only what he showed
me), have also been obtained in similar situations by Mr. Minakata
in Japan. Whether the moist climate of Aberdeenshire is
especially favourable to the growth of Mycetozoa living in such
exposed situations, or whether Mr. Cran's success is due to
his superior powers of observation, I cannot say; but I confess
that, after this lesson, I came south determined to search the
trunks of living trees, and, up to the present time, my efforts,
though not entirely fruitless, have yielded but small results.
A list of the arboreal Mycetozoa that we know of (thirty-six
species in all) will be found at the end of this paper ; in it are
included those on living wood only, and not species growing
on dead limbs of living trees.
Dead Leaves.- Turning now to the species occurring on
dead leaves, we find their number is so large, and their appearing