inclosing boundary. We seem to feel the need of some answering line or
re-echo in the character of the composition to the shape of its
boundary, to give it its distinctive reason for existence in that
particular form--just as we should expect a shell-fish to conform to the
shape of its shell. Such a re-echo or acknowledgment might be ever so
slight, or might be quite emphatic and dominate as the leading motive,
but for perfectly harmonious effect it must be there.

[Illustration (f064): Relation of Design to Boundary: Simple Linear
Motives and Pattern Bases.]

A strictly simple and logical linear filling of such spaces might be
expressed in the most primitive way, as in the illustration on p.
109[f064].

By these means certain primitive types of ornament are evolved, such as
the Greek volute and the Greek key or fret, the logical ornament of a
logical people.

Such arrangements of line form simple linear patterns, and a decorative
effect of surface is produced simply by their repetition, especially if
the principle of alternation be observed. This principle may be
expressed by taking, say, a series of squares or circles, and placing
them either in a line as for a border arrangement, or for extension
vertically and laterally over a surface, and filling only the alternate
square or circle, leaving the alternate ones, or dropping them out
altogether (see illustration, p. 111[f065]).

[Illustration (f065): Use of Intervals in Repeating the Same Ornamental
Units.]

When we desire to go beyond such primitive linear ornaments, however,
and introduce natural form, we should still be guided by the same
principles, if we desire to produce a strictly decorative effect, while
varying them in application to any extent.

It matters not what forms we deal with, floral, animal, human; directly
we come to combine them in a design, to control them by a boundary, to
inclose them in a space, we shall feel this necessity of controlling
line, which, however concealed, is yet essential to bring them into that
harmonious relation which is the essence of all design (see
illustration, p. 112[f066]).

[Illustration (f066): Designs of Floral, Human, and Animal Forms,
Governed by Shape of Inclosing Boundary.]

We may take it as a general rule that the more purely ornamental the
purpose of our design, and the more abstract in form it is, the more
emphatically we may carry out the principle of correspondence of line
between that of the in