INTRODUCTION 3 



The greatest taxonomic advance since Fries is embodied in the 

 monographic treatment of Rostafinski, whose "Versuch" of 1873 was 

 followed by the monograph of 1875 and its supplement of 1876. 

 Rostafinski, a pupil of de Bary, followed that student's example of 

 making intensive use of the microscope, at that time, of course, 

 greatly improved over the crude instruments at the command of the 

 earlier workers, although much inferior to modern apochromatic and 

 immersion lenses. The monograph and supplement, written in Polish, 

 were largely inaccessible to students in other countries, but were made 

 available to English-speaking workers to a considerable extent by 

 the works of Cooke. In 1892 Massee published his monograph, based 

 on Rostafinski, but departing in many particulars from his treatment, 

 and greatly increasing the number of recognized species, not infre- 

 quently on an insufficient basis. Two years later appeared the first 

 edition of the standard English monograph, A. Lister's "Mycetozoa," 

 revised in 1911 and again in 1925 by his daughter, Miss G. Lister. 

 The illustrations in this work, many of them in natural colors in the 

 later editions, have never been surpassed in comprehensiveness and in 

 general accuracy, and it is not surprising that European treatments in 

 other languages have largely been modelled upon this excellent work. 



In North America the first extensive collections and reports were 

 made by Schweinitz (1822; 1832). Later active collectors were Curtis, 

 Ravenel, Ellis, Peck, Farlow, Morgan, Rex, Wingate, Thaxter, Bethel, 

 Sturgis and Bilgram. Cooke, in 1877, published the first general ac- 

 count of the slime molds of the United States, followed by that of 

 Morgan (1893-1895). The account of the slime molds of eastern Iowa 

 (1892) and of Nicaragua (1893) by Macbride, preceded the first edition 

 of his North American Slime-Moulds (1899). The greatly enlarged 

 and emended second edition of this work (1922) is the basis for the 

 present study. 



As already mentioned, there has been no general agreement as to the 

 limits of the Myxomycetes, nor is there one at present. A number of 

 groups of doubtful position have been regarded as related to the slime 

 molds by some authors, but excluded by others. De Bary, as already 

 noted, included the Acrasieas. This curious group of organisms, first 

 studied by van Tieghem, resembles the Myxomycetes in the possession 

 of a naked amoeboid stage, but its members possess neither swarm- 

 spores nor a true Plasmodium. Just before fructification the amoebae 

 become aggregated but do not lose their individual identity; can, in 

 fact, readily be shaken apart in water. Their resemblance to the 

 Myxomycetes seems to be superficial only, and most recent workers 

 have been inclined to doubt their close relationship. 



