I. The colors of the Thallus and apothecia of Lichens—­their causes, and
      the circumstances which modify and alter them.

  II.  History of the application of their coloring matters to the art of dyeing.

 III.  Chemical nature and general properties of these coloring matters.

  IV.  Tests and processes for estimating qualitatively, and quantitatively the
      colorific powers of individual species—­with their practical applications.

   V. Processes of manufacture of the Lichen-dyes, on the large and small
      scale in different countries—­with the principles on which they are founded.

  VI.  Nomenclature of the dye-Lichens, and of the Lichen-dyes.

 VII.  Botanical and commercial sources of the same.

VIII.  Special applications of the Lichen-dyes in the arts.

  IX.  Commercial value of the dye-Lichens, and their products.

   X. Geographical distribution of the dye-Lichens—­with the effect of climate;
      situation, &c., on their colorific materials.

    Of the four first sections of his paper, the following is a very
    short summary or synopsis:—­

Under the first head, the author spoke of chlorophylle and various organic and inorganic substances, which enter into the formation of the colors of the thallus and apothecia of lichens, and of the modifications of these colors depending on various degrees of—­1.  Exposure to air and light. 2.  Temperature. 3.  Moisture, &c. 4.  Atmospheric vicissitudes. 5.  Season of the year. 6.  Nature of the Gonidic reproduction (i.e., gemmation). 7.  Nature of habitat. 8.  Organic decomposition. 9.  Coalescence of parts, monstrosities, &c.

Under the second section, he traced historically the manufacture of Lichen-dyes, and the native use of Lichens as dye agents, among different nations, from the times of Theophrastus, Dioscorides, and Pliny, down to the present day, sketching briefly the ancient end modern history of orchil, cudbear, and litmus, and specifying the native use of lichen-dyes in different, countries of Europe, Asia, and America.  He alluded more particularly to their application to the dyeing of yarns, &c., by the Scotch Highlanders, under the name of “Crottles.”  “The process of the manufacture of the various crottles, generally consisted in macerating the powdered lichen for two or three weeks, in stale urine, exposing the mass freely to the air by repeated stirring, and adding lime, salt, alum, or argillaceous and other substances, either to heighten the color or impart consistence.  To such an extent did this custom at one time prevail, that, in several of our northern counties each farm and cottage had its tank or barrel of putrefying urine, a homely but perfectly efficient mode of generating the necessary amount of ammonia.  In the county of Aberdeen, in particular, every homestead