point out the reasons why all charts and maps should be based upon the decimal system of scales. Experience will furnish the very best of arguments. =232. Color scheme.= The first requisite for the graphic representation of formations, regions, etc., is that each class of formations be invariably indicated by the same color. It is also necessary that the colors and shades be easily distinguishable, and it is at least desirable that they be referred to the different classes in some consistent sequence. Uniformity in all these points is greatly to be desired at the hands of all ecologists. Here, as in the case of the standard scale, uniformity will be found the more desirable the more impossible it is made by ignoring it. In the use of color to represent regions and provinces, on maps too small to indicate formations, the color of each division is represented by the color of its dominant formation; thus the prairie province is colored ochroleucus on account of the color used to represent prairie formations, the boreal-subalpine zone atrovirens on account of the typical coniferous forests, etc. No endeavor has been made to take account of the various types of formations, e. g., the different coniferous forests, as this is a problem to be worked out for more local maps in various shades of dark green, etc. The following color scheme which has been based upon the points made above is proposed as a satisfactory solution of the problem. The color standard used is that of Saccardo’s Chromotaxia. I. Hydrophytic Formations: _blue_ 1. Marine: _cyaneus_ 2. Brackish: _ardesiacus_ 3. Freshwater: _caeruleus_ 4. Swamps and marshes: _caesius_ II. Mesophytic Formations A. Forest formations: _green_ 1. Coniferous forests: _atrovirens_ 2. Broadleaved evergreen forests: _viridis_ 3. Deciduous forests: _flavovirens_ B. Grassland formations: _yellow_ 1. Meadows: _melleus_ 2. Prairies: _ochroleucus_ C. Culture and waste formations: _red_ 1. Fields: _ruber_ 2. Groves and orchards: _atropurpureus_ 3. Wastes: _purpureus_ III. Xerophytic Formations: _brown_ 1. Deserts: _isabellinus_ 2. Plains and steppes: _avellaneus_ 3. Saline formations: _umbrinus_ 4. Arctic-alpine formations: _testaceus_