Since the genus Botrychium was last revised (Clausen, 1938), much research on it has been done, and many of our taxonomic ideas concerning the use of infraspecific categories (subspecies, variety, form) have changed (Wagner, 1960). Many Botrychium species can be distinguished only by subtle differences, and there is often high level of variability, even in single populations. In the little Moonworts, Botrychium subg. Botrychium, taxonomic difficulties are exacerbated by the small size of the plants and the tendency for the segments to become folded when pressed. To gain an idea of the distinctness of the species, careful field studies of sizeable populations are needed, and the specimens must be pressed so as to spread out the segments. Finding these usually rare and local plants requires a labor of love. Together with colleagues and students, we have spent an extaordinary amount of time exploring for Moonworts over the past several decades. Some of the fruits of this quest are described here. In making our taxonomic judgments, we have adhered to strict requirement of consistency. Plants from one locality to another must display the same characteristics. Likewise, the differences from other species must be consistent; there should be no connecting forms. We have emphasized the ability of two critical taxa to occur together in the same habitats without intergrading. Mixed populations have thus been of value in making decisions. We also have used the method of mutual associations-the ability of two taxa to maintain their differences in their separate habitats, even though their mutually associated relatives stay alike. Thus if taxon A grows with taxon C in one habitat, and taxon B grows with C in another, and if taxon C remains uniform in both habitats, then the differences between A and B are probably genetically fixed. The four new Moonworts described here have been studied in wild populations, and in all cases the evidence upholds their validity as discrete species. We treat each only briefly, but we hope that the description and comments will give other workers preliminary idea of their distinctions and also will lead to finding new populations. More detailed reports on all of these plants will be made in the future. The measurements are based upon the best-developed and most distinctive specimens from each of several collections. Small specimens may be hard to identify, and all of these species include tiny fertile individuals less than 3 cm tall. Spores were mounted in Hoyer's solution (Beeks, 1955) and measured along the largest diameter. The ranges represent the averages of several different collections.