Piling up of identical or similar forms occurs in nature as often as lateral symmetry. Plants with their vertical succession of leaves, branches of trees, piles of stones, ranges of mountains rising behind one another, may suggest vertical arrangements of similar elements. However, much more common are repetitions in horizontal bands; of simple arrangements of single strokes in rows; and of complicated successions of series of varied figures that recur in regular order (fig. 48, Plate V). It follows from what has been said before that the forms here discussed are not expressive of specific emotional states and in this sense significant. This conclusion may be corroborated by a further examination of decorative forms. [Illustration: PLATE V. Kumiss Goblets of the Yakut.] We have already indicated that the artistic value of an object is not due to the form alone, but that the method of manufacture gives to the surface an artistic quality, either through its smoothness or through a patterning that results from the technical processes employed. However, the treatment of the surface is not controlled solely by technical processes. We may observe that in the art products of people the world over other elements occur that are due to the attempt to emphasize the form. [Illustration: Fig. 48. Pottery vessels: _a_ Finland; _b_ Ica, Peru.] The application of marginal patterns is one of the most common methods employed for this purpose. In many cases these are technically determined. When, for instance, a woven basket is finished off, it is necessary to fasten the loose strands and this leads generally to a change of form and surface pattern in the rim. The strands may be turned down, wrapped and sewed together, they may be braided, or woven together and left standing as a fringe. In a bark basket the rim must be strengthened by a band, to prevent splitting of the bark, and the band and the sewing set off the rim from the body. A thin metal disk may have to be strengthened by rolling in the outer rim. [Illustration: Fig. 49. Birchbark vessels; _a_, _b_, Amur River; _c_, Shuswap; _d_, _e_, Alaska.]