1884. Raciborski, M. Myxomycetes Agri Krakov. Genera, Species et Varietates novae. 1888. Raunkiaer, C. Myxomycetes Daniae. 1769. Retzius, A. J. In Handlungen, Kon. Svensk. Vet. Acad. 1890. Rex, George A. In Proceedings Philad. Acad. of Nat. Sciences--to 1893. 1873. Rostafinski, J. Versuch eines Systems der Mycetozoen. 1875. Rostafinski, J. Sluzowce Monografia. 1778. Roth, A. W. Tentamen Florae Germanicae. 1888. Saccardo, P. A. Sylloge Fungorum, vol. vii., _et seq._ 1841. Sauter, A. Flora, vol. xxiv., p. 316. 1762. Schaeffer, J. C. Fungi qui in Bav. et Pal. nascuntur--to 1774. 1797. Schrader, H. A. Nova Genera Plantarum. 1890. Schroeter, J. Myxomycetes, in Engler u. Prantl Pflanzenfamilien. 1885. Schroeter, J. Kryptogamenflora von Schlesien, die Pilze. 1801. Schumacher, C. F. Enumeratio Plant. Saell. crescentium. 1805. Albertini, I. and Schweinitz, L. D. de. Conspectus Fungorum. 1822. Schweinitz, L. D. de. Synopsis Fungorum Car. Sup. 1834. Schweinitz, L. D. de. Synopsis Fungorum in America Boreali. 1797. Sowerby, J. English Fungi--to 1809; 3 vols. 1760. Scopoli, J. A. Flora Carniolica--to 1772. 1797. Trentepohl, K. Observations Botanicae,--to Roth, Catalecta Botanica, Fasc. i. 1833. Wallroth, C. F. Flora Cryptogamica Germaniae. 1787. Willdenow, K. L. Florae Berolinensis Prodromus. 1886. Wingate, Harold, Jour. Mycol. ii., 125. 1889. Wingate Harold, In Proc. Acad. Nat. Sci. Philad. 1890. Wingate, Harold--in Revue Mycologique. 1873. Woronin u. Famintzin, Ueber Zwei neuen Formen von Schleimpilzen. 1885. Zopf, W. Die Pilzthiere oder Schleimpilze. To these may be added the many contributions on the general subject, as these are found in all sorts of current botanical literature; cited everywhere in this volume as occasion offered. INTRODUCTORY The Myxomycetes, or slime-moulds, include certain very delicate and extremely beautiful fungus-like organisms common in all the moist and wooded regions of the earth. Deriving sustenance, as they for the most part do, in connection with the decomposition of organic matter, they are usually to be found upon or near decaying logs, sticks, leaves, and other masses of vegetable detritus, wherever the quantity of such material is sufficient to insure continuous moisture. In fruit, however, as will appear hereafter, slime-moulds may occur on objects of any and every sort. Their minuteness retires them from ordinary ken; but such is the extreme beauty of their microscopic structure, such the exceeding interest of their life-history, that for many years enthusiastic students have found the group one of peculiar fascination, in some respects, at least, the most interesting and remarkable that falls beneath our lens.