Old- Liviiif^ Resources — Plants 



201 



species to light. Between 1975 and 1989. for 

 example. 725 new taxa of vascular plants were 

 reported from the conterminous United States 

 alone (Hailman 1990). 



The following discussions indicate what 

 published plant information and data bases exist 

 and describe the level of current and historical 

 plant collecting in the United States. 



Major Plant Groups 



Few families or genera in the United Slates 

 have been studied comprehensively throughout 

 their range during the past 50 years, and until 

 now there has been no source that brings togeth- 

 er the best existing knowledge of U.S. plant 

 taxa. To provide such a resource, plant taxono- 

 mists from the United States and Canada have 

 established the Flora of North America project. 

 Scientific information on the names, relation- 

 ships, characteristics, and distributions of all 

 plants that grow outside of cultivation in North 

 America noilh of Mexico will be published in 

 14 volumes and in an online data base over the 

 next 8 years. To date, two volumes have been 

 published (Flora of North America Editorial 

 Committee 1993). As infoimation is synthe- 

 sized and published, research needs can be 

 evaluated. Checklists of North American plants 

 are currently available (Soil Conservation 

 Service 1982: Kartcsz 1994), and the Soil 

 Conservation Service maintains a data base of 

 Plant List of Attributes. Nomenclature. 

 Taxonomy, and Symbols (PLANTS) for North 

 America. 



Pteridophytes 



About 500 species of ferns and fern allies 

 are found in the United States, excluding 

 Hawaii where about 200 occur. The most recent 

 treatment of ferns for North America is in 

 Volume 2 of Flora of North America (Flora of 

 North America Editorial Committee 1993). 

 Recent studies involving DNA analysis, 

 isozyme work, and modem statistical analyses 

 have significantly improved our understanding 

 of genetic relationships among groups of ferns 

 (Wagner and Smith 1993). Fern groups in the 

 dry areas of the Southwest especially need 

 study. 



Gymnosperms 



Gymnosperms. with 118 species (none 

 native to Hawaii), include the economically 

 important conifers. Tremendous research has 

 been done on conifers, including detailed popu- 

 lation studies of individual species. The most 

 recent treatment of gymnosperms for North 

 America is Volume 2 of Flora of North America 

 (Flora of North America Editorial Committee 



1993). The Atlas of United States Trees (Little 

 1971). although somewhat outdated, is still the 

 best source for precise distributional informa- 

 tion for conifers. 



Angiosperms 



Most vascular plant species in the United 

 States are angiosperms. those plants bearing 

 what are commonly recognized as flowers. The 

 large sunflower family has been intensively 

 studied over the past several decades, although 

 work on this family is hampered by its com- 

 plexity and the difficulty of identifying individ- 

 ual plants. In addition, more extensive survey- 

 ing of the Southwest is needed to understand the 

 family. An account of Asteraceae for the south- 

 eastern United States was published in The 

 Vascular Flora of the Southeastern United 

 States (Radford et al. 1980): Great Basin 

 species are treated in Volume 5 of the 

 Intermountain Flora (Cronquist et al. 1972-94), 

 and Asteraceae will appear as the final pub- 

 lished volume of Flora of North America. 



The grass family is the most agriculturally 

 important family in the United States, both for 

 its forage value and as a source for crop and 

 rangeland weeds. Researchers coordinated by 

 Utah State University are revising the Manual 

 of the Grasses of the United States (Hitchcock 

 and Chase 1950). 



Much work on the complex legume family 

 has been done by researchers in the U.S. 

 Department of Agriculture. Genera such as 

 Astragalus, with more than 325 species, still 

 require tremendous work to understand: it is 

 extremely difficult to identify individual 

 species. An international program to develop a 

 checklist of species in this family, with distrib- 

 ution, growth habit, and economic infonnation. 

 is being carried out by the International Legume 

 Data Information System (ILDIS): the Missouri 

 Botanical Garden is the center for North 

 American information for this project. 



The sedge family includes ecologically 

 important species, especially in wetlands where 

 sedges dominate. Although sedges are being 

 intensively studied, individual species can be 

 difficult to identify; Carex alone contains more 

 than 400 species. Cyperaceae specialists have 

 been collaborating on common solutions to tax- 

 onomic problems in this group: volume 1 1 of 

 Flora of North America will synthesize the best 

 information available on the family. 



Regional Floras 



Hawaii 



The Manual of the Flowering Plants of 

 Hawaii (Wagner et al. 1990) gives excellent 

 coverage for flowering plants. Two fern tloras 



Sclenii cilatu. a meniher ol Ihe 

 sedge family. Cyperaceae. 



The fern Cyrlomium falcatum. 



