We find in Paul Klee's Notebooks:


A leaf is a part of the whole. If the tree is an organism, the leaf is an organ. These small
parts of the whole are again articulated in themselves. In this articulation, articulate ideas
and relations prevail that reflect on a small scale the articulation of the whole... Leaf, stem,
and veins belong together, especially stem and central vein, indeed, the central vein may
be described as a continuation of the stem. this whole line is thus divided into stem and
stem continuation. The subdivisions of this line are ever different in the different leaves, but
even division is certainly rarer than uneven... the lateral veins, moreover, undergo their
own articulation by measure and weight. The same applies to their further branchings on
both sides. The intervals and the dynamic forces dwindle to the point of no return. The
tracing eye can no longer distinguish the last ramifications as lines and abandons the
pursuit. The particles become confusingly small and are sensed as planar elements rather
than linear forces... The planar massiveness is the element that to the eye no longer
appears linear, but is distinguished as a separate element by its tangle of lines. As against
linear definition, this element may create an impression of softness. This line system
reaches into the other element, finely forked or sievelike, and enough of it sticks. The
planar form that arises is then independent of the inreaching linear radiation. And where
linear power ends, there arises contour, the limit of planar form...

The linear forces gather within it [the tree] to form a powerful stream, and they radiate
outwards, in order to pervade the air space at free height. Henceforward articulation
naturally becomes more and more ramified and open, to make the best of air and light.
Leaves become flat lobes, the whole thing begins to resemble a lung or gills, porous,
subdivided, for a single purpose.

Let this entire organism now become an example to us- a structure functioning from within
to without or vice versa.

Let us learn: The whole form results from a single base, the base of inner necessity. Need
is at the bottom.

There is no random toying with results. The active path towards form and inner structure is
ineluctable. Considering the articulation on its own and recalling the leaf, we can observe
successive changes in the character of articulation, as we move from the main limb to the
side limbs. Beginning with the element of singularity we arrive at the character of plurality.
In terms of form production, the line between linear and two-dimensional elements must lie
somewhere...


 

We can apply this structural analysis to human consciousness and use either "mind" or the
central nervous system as the primary trunk line, the branches of which extend from the
nervous system into the objects of perception, becoming a finer and finer cloud as
we approach the point at which "the tracing eye can no longer distinguish the last ramifications
as lines and abandons the pursuit
". Beyond the soft tangle of rustling leaves lies the realm of
the invisible the silent and the unknown. That liminal area between the linear trunk of self
and the planar cloud of perceptions shifts constantly with perceptual attention. That shifting
border alone defines selfhood, a shell to which new perceptual territories are claimed for
the self by subconscious desires and habitual proclivities. Even the tip of the leaf of a tree
senses the sun and the wind, so the consciousness aggregate that constitutes the
perceptual territory of the leaf is quite vast (i.e. extending at least to the center of the solar
system) despite its limited perceptual apparatus. A focused human mind, trained not to
"abandon the pursuit" could potentially follow the branches of consciousness much more
deeply into the space in which it is embedded, extending the linear "self" further into the
cloud of external reality than would seem possible in ordinary experience. "Henceforward,
articulation naturally becomes more and more ramified and open... the whole thing begins
to resemble a lung or gills, porous, subdivided, for a single purpose."