surface extends horizontally and vertically, but the vertical
extension seems to assert itself most to the eye.

Any arrangement of lines of the trellis or diaper order logically covers
a wall surface, and may be appropriately used as a basis for a wall
pattern, whether merely to mark the positions of a simple spray or
formal sprig pattern, or as a ground-plan for a completely filled field
of repeating ornament, whether painted, stencilled, or in the form of
wall-paper or textile hanging.

In the simple geometric net of squares or diamonds or circles, however,
there is nothing that emphatically marks adaptability to a vertical
position. Such plans in themselves are equally appropriate to the floor
in the form of paving and parquet. The ogee plan, however, and its
variant, the vertical serpentine or spiral plan, at once suggest
vertical extension, the former perhaps by its leaf-like points arranging
themselves scale-wise, and the latter by its suggestion of ascending
movement.

It is noteworthy that in the course of the historic evolution of mural
decoration, designs based upon these systems constantly recur. They are
part of the pattern-designer's vocabulary of line, and among the
principal, though simplest, terms by which he is able to express
vertical extension.

The question of _scale_ in designing mural decoration of any sort is
very important. This demands a certain power of realizing the effect of
certain lines and masses if carried out, and the relation of one part to
another as well as to the dimensions of the walls and the room itself.
Here, as indeed throughout art, a reference to the human figure will
give us our key, since after all decoration goes to form a background
for humanity. With natural flowers and leaves it is always right to
design for mural purposes on the same scale as nature.

[Illustration (f121): Diagram Showing the Principal Fundamental Plans or
Systems of Line Governing Mural Spacing and Decorative Distribution.]

[Scale]

Scale in design should be also considered in relation to the general
character of a building and its purpose, the use and lighting of a
living room: its dimensions and proportions, and relation to other
rooms. There is great range for individual taste and fancy.

The artist would naturally look to the capacity of the space which he
had to decorate, and what it suggested to his mind. He might want