Upon reconsideration, however, it was decided to use the political boundaries 

 of those states that are considered to make up southwestern United States as the 

 boundaries of our project area; namely, Oklahoma, Texas, New Mexico and 

 Arizona. Since there is some interplay of species where the eastern forests and the 

 western prairies join, it was thought best to incorporate these forest areas. Their 

 inclusion augmented considerably the number of wetland plants, as well as strictly 

 aquatics, to be treated in our research. It was our opinion that the inclusion of 

 species in these forested regions would make our work not only more useful in 

 the states covered by our research but also of some use to those states to the east 

 and northeast of our area. We also considered that since the greater part of the 

 water that is found in the lower, more arid regions is derived not so much from 

 rainfall but from springs and snowfields, and other such places found in the high 

 mountains, the montane vegetation that is associated with these water sources 

 should also be included. The inclusion of these plants of primarily seepage areas 

 that are usually confined to high mountain regions further augmented the species 

 that we were to treat. 



This project was originally visualized, in early 1963, to be a taxonomic-ecologlc 

 treatment, but after more than a year of vainly searching for an interested quah- 

 fied ecologist to work on the project the ecological phase was reduced to what the 

 taxonomists could contribute. Today, considering that "ecology" and "environ- 

 ment" are so popular with almost everyone and with nearly all phases of our life, 

 it seems unthinkable that, in 1963, we were unable to convince those ecologically- 

 minded and -trained individuals whom we approached to take part in this project. 

 We received only resistance from prospective applicants — everything from not 

 wanting to get their feet wet, not wanting to do field work, not interested in 

 working on aquatic plants, to "what is the need and use of doing this research?" 

 Needless to say, we were disappointed by such lack of interest. In spite of this 

 discouragement, a great amount of ecological and environmenal information was 

 gained by our own observations that was supplemented by pertinent information 

 found in literature. 



Nevertheless, this work does not pretend to be a study of the ecology of hydro- 

 phytes nor of their complex physiology and morphology. Rather, it is an attempt 

 to present a taxonomic treatment of the species that comprise what we know as 

 hydrophytes without degenerating "into a tedious floristic catalogue," as abhorred 

 by Sculthorpe (1967) and others. 



Since no ecological studies, as such, were undertaken, field work, except in 

 selected localities, consisted primarily in what might be termed a random sampling 

 of various types of habitats located throughout the region covered. Locations 

 would be visited, often more than once during any one season, observations 

 recorded, and herbarium vouchers prepared. Approximately 9,000 field collections 

 were made during the course of the work, the first set of which is in the Herbarium 

 of Texas Research Foundation (LL), Renner, Texas. Additional specimens are 

 in the Gray Herbarium (GH) of Harvard University, The University of California 

 Herbarium (UC) at Berkeley, Rancho Santa Ana Botanic Garden Herbarium 

 (RSA) in California, Florida State University Herbarium (FSU), Tallahassee, 

 and elsewhere. 



Distribution information within our area of study is based primarily upon the 

 9,000 botanical vouchers that were collected during the course of this project, 

 and upon those that were examined, where possible, in various herbaria. These 

 distribution data are supplemented by a discriminate and judicial adaptation of 

 distributional information provided by published monographs, revisions, Floras 

 and other such basic literature that are included in our Bibliography. 



ix 



