THE ARTISTIC ANATOMY OF TREES

BY JOHN W. HARSHBERGER

Professor of Botany

Light Values.-The person with the artistic sense has been impressed probably by the form of trees and the tracery of their branches, as outlined against the sky. Not only is the the tree silhouetted in this manner, but the color of the sky, the character and position of the clouds and the location and nature of the surrounding objects all form part of the picture. The appearance of the tree, or trees, under observation changes with the illumination. The tree in strong sunlight has an entirely different light value from a tree seen at sunrise, at sunset, on a day partially overcast, or on a cloudy day, while it is quite distinct on a day of rainfall. The color value of the tree is also quite different in the moonlight, or where it is lighted by a nearby electric arc. The visual impression, which the tree produces, also varies with the compass direction, whether it is against the northern, southern, eastern, or western sky, as a background. The Zuni Indians appreciated this light relationship, for they named their ceremonial maize, as follows: Thluptsi-kwa (yellow medicine corn) symbolic of westland and spring; Shi-lo-a-kwa (red medicine corn) symbolic of southland and summer; K' ó ha-kwa (white medicine corn) symbolic of eastland (dawnland) and autumn; Ku'-tsu-a kwa (speckled medicine corn) the corn of skyland and daylight. The aspect of any given tree is different in winter, especially if covered with clinging snow, or imbedded in crystal ice after a sleet storm, or when coated with the rime of hoar frost. The shadow, which the arboreal specimen casts, should not be neglected in this consideration of the effect made upon the visual sense organs, and this changes with the season of the year and the time of day. The tree shadow is longer in the

middle of the day at the winter solstice, than at the summer solstice. The long shadows cast with the declining sun have been often the subject of remark, when after the heated spell of the summer day the cool of the evening entices one to enjoy the great out-of doors.

Appeal of Study.-A study of artistic details of this description should appeal strongly to the color artist, the painter, the landscape architect and the lover of nature. The painter tries to convey his impressions of the scene of sylvan grandeur to his canvas by the employment of colors by which he emphasizes his interpretation of the color scheme and the light and shade values. The landscape architect attempts to assemble his trees and shrubs so as to interpret nature, and in accomplishing this, he must familiarize himself with the materials which he uses. He must know his trees and shrubs in their spring, summer, autumn and winter condition, their outline their colors, their flowering and leafing periods, their size and other details, which might influence the harmony of his landscape composition. The color of the foliage in spring, summer and autumn must be considered by the landscape gardener, if he desires to interpret nature. It should appeal to the poet and the naturalist, who delight to study the varying moods of nature. The delight of a ramble in the country during the winter may be increased greatly by a recognition of the trees with upright trunks and bare branches. It is gratifying to be able to recognize, the specific characters of the trees met with on such a walk, and there are trees which are distinguished at a distance, such as the Lombardy poplar, the birch, the beech, the sycamore and the elm. On nearer approach, others may be noted by their habit of branching and by the appearance of their bark.

Practical Importance.-As this matter is of much practical importance to artists, photographers, designers of landscapes, gardeners, painters and the educated public in general, a more intimate study of the artistic anatomy of trees is given herewith. Trees form especially suitable objects for out-door study and they are available in city and country, in

winter and summer. It is interesting to sit back in a room and study the trees as framed in by the window. The writer with the object of outlining the elements, which enter into the composition of the display exhibits in some of our large museums of natural history, has made sketches of bits of natural landscapes as seen framed by the window. Photographs also accomplish the same purpose, for the photograph is a selected bit of landscape, which more accurately depicts the size and relationship of natural objects better than a pencil drawing ever can do. The successful photographer of nature must be a man with a trained artistic sense.

Deliquescent and Excurrent Stems.-There is a familiar classification of trees into those with deliquescent and excurrent stems. In the deliquescent stem, the tree branches repeatedly, year after year, so that the trunk is soon lost in the branches. The common American elm is a good illustration. The excurrent stems, exemplified in the firs and the spruces of spire-shape, are those which grow upward from a terminal bud, so that there is formed a single uninterrupted shaft. Many coniferous trees are typical of this kind of growth. Another classification is whether the plant is a tree, or a shrub. A shrub is a woody plant with a number of branches of equal strength arising from the same root system close to the ground, while a tree is an arborescent growth with the branches subsidiary to a main stem, if in an undeveloped condition, as a sapling, or possessing a main trunk, or bole, with the branches given off at some distance above the ground.

Deciduous and Evergreen Trees.-A distinction has been made also between deciduous trees and evergreen trees. These are purely relative terms, for we understand by a deciduous tree one which casts off its foliage leaves annually with the approach of the winter, while many evergreen trees are only relatively so, because the leaves are dropped periodically after the lapse of two, three or more years, but usually in such cases the old leaves are not completely lost until new ones have appeared to replace them. The deciduous trees are known also as the broad-leaved trees, because their leaves,

as a rule, are broad and flat. They are known as summergreen trees, because clothed with verdure in summer, and as tropophytes, because alternately leafy and active in summer and leafless and inactive in winter.

Bases of Trees. In architecture we distinguish the elements which enter into the building. There are the bricks, the plaster, the ornaments, the rafters, the pieces of slate, the tiles, the iron grills and other details which must be combined by the builder into an artistic whole. The botanist recognizes also and has named the parts of the different kinds of trees. The base of the tree trunk may swell out toward the roots, so that an enlarged base is produced. This is typical of trees which grow in swamps with the ground wholly, or partially, covered with water. Enlarged bases may be due to buttresses developed as flying projections and which extend outwardly in all directions as a pedestal rendering the tree more stable. The ceiba (Eriodendron anfractuosum) described by Kingsley in his "At Last" is perhaps the best illustration of a tree with a buttressed base, for the inhabitants of the West Indies, where the species is native, use the spaces between the flat extended buttresses as stalls for their horses and cattle. There are two forms of deciduous cypresses in the swampy districts of the southern states. The common cypress (Taxodium distichum) has sharp-edged basal ridges, while the other species (T. imbricarium), usually found in undrained swamps, has rounded buttresses. Both the ceiba and deciduous cypress are adapted to growth in countries visited by tropical hurricanes, although their buttresses were not developed because of the visitation of such storms, for it was demonstrated a few years ago at the Missouri Botanical Garden in St. Louis that such trees were not injured by tornadoes, while the Eads Bridge and many other trees were damaged badly. Species of the genus Sterculia in the East Indies also show buttressed bases, as depicted in the published journals of botanical travellers.

Roots of Trees. To be considered at this point are the trees which give off a mass of roots which serve to brace, or