190 



Plants — Our Livini; Ri'stnirces 



Even though the bulk of information about 

 our native vascular flora was collected in the 19th 

 and early 20th centuries, significant data about 

 the status of plants in the United States continue 

 to be collected as species expand their ranges, as 

 other species thought locally extiipated are redis- 

 covered, as poorly surveyed areas are explored, 

 and as species become extinct. Even in states like 

 New York, which has a long and cunently active 

 program of botanical exploration, additional 

 species of vascular plants continue to be docu- 

 mented as poorly surveyed areas are given more 

 comprehensive coverage (Miller and Mitchell, 

 this section!. 



Herbaria and museums continue to be impor- 

 tant repositories for this information because 

 collecting by their personnel represents a signif- 

 icant effort at inventorying plant and fungal 

 species in this country (Morin, this section). 

 Unfortunately, their role is increasingly at risk as 

 support for collecting declines. In other ca.ses, a 

 shortage of trained specialists will prevent an 

 adequate inventory of biotic diversity. Although 

 many regional checklists exist as well as excel- 

 lent manuals that cover bryophyte systematics, 

 floristic inventories of bryophytes have been 

 hampered primarily by a lack of trained profes- 

 sionals (Merrill, this section). 



The flora of the American countryside has 

 been much changed since European settlement. 

 Over the past 20 years alone, more than 200 

 species of non-native vascular plants have been 

 recorded in New York state; these species repre- 

 .sent an important risk to native plant communi- 

 ties (Miller and Mitchell, this section). Human 

 activities are responsible for the introduction of 

 these invasive exotics as well as the extinction of 

 some species with small geographic ranges or 



those restricted to unique habitats. 



If cuiTent trends in land-use continue, how- 

 ever, even species with more widespread distri- 

 butions will be at risk. For example, lichens as a 

 group are declining in many areas from the 

 effects of air pollution. It is estimated that as 

 much as 80% -90% of the original lichen flora 

 has disappeared from urbanized areas (Bennett, 

 this section). Likewise, marked declines in 

 macrofungi have been documented in Europe 

 although similar trends in this country have not 

 been published because, in part, of the incom- 

 plete inventory and lack of monitoring of these 

 groups in the United States (Mueller, this sec- 

 tion). Among the more completely documented 

 vascular plants. The Nature Conservancy reports 

 that 9.8% of native species have been lost from 

 at least one state, more than 200 native species 

 have become extinct in the United States, and an 

 additional 403 native plant taxa need protection 

 under the United States Endangered Species Act 

 (Morse et al., this section). 



The articles in this section represent an 

 important step in describing the status of the 

 plant and lungal taxa in this country. They pro- 

 vide a snapshot illustrating our knowledge of 

 past and current distributions of plants; the 

 importance of developing a more comprehen- 

 sive data base for various groups, especially the 

 fungi; and the need to develop a comprehensive 

 inventory of the continually changing and evolv- 

 ing flora of the United States. If we are to under- 

 stand the causes underlying the changes in pat- 

 terns of diversity and make predictions about the 

 threats of anthropogenic (human-caused) activi- 

 ties, we must have a quantitative understanding 

 about the nature and distribution of the taxa 

 composing our flora. 



Microfungi: 

 Molds, 

 Mildews, 

 Rusts, and 

 Smuts 



Amy Y. Rossman 



U.S. Department of 



Agriculture 



Fungi are a group of organisms that exist as a 

 vast network of tiny threads growing in and 

 out of all kinds of organic matter. As they grow. 

 the threads secrete enzymes that break down the 

 substances around them, releasing nutrients into 

 the environment. Without fungi, the world would 

 be completely covered with organic debris that 

 would not rot, and nutrients would not be avail- 

 able for plant growth. All plants would die. 



Microfungi include the organisms that are 

 called molds and mildews as well as rusts and 

 smuts, which cause plant diseases. They grow in 

 all substrates, including plants, soil, water, 

 insects, cows' rumen {see glossary), hair, and 

 skin. Microfungi are said to be small because 

 only part of the fungus is visible at one time, if 

 at all. The visible parts produce thousands of 

 tiny spores that are carried by the air, spreading 

 the fungus. Most of the fungal body consists of 

 microscopic threads extending through the sub- 

 strate in which it grows. The invisible fungal 



structure may be extremely large, often extend- 

 ing for miles as, for example, the "humongous 

 fungus"" occurring in the north-central United 

 States (Rensberger 1992). 



Among the multitudinous molds are humble 

 servants such as Penicillutm notatiim, the source 

 of penicillin, and Tolyposporium niveiim. a pro- 

 ducer of cyclosporin, the immune-system sup- 

 pressant used for organ transplant operations. In 

 sustainable agriculture the fungal performers are 

 agents of biological control and crop nutrition, 

 helping the environment through the reduced 

 use of chemical pesticides and fertilizers. Fungi 

 can stop a hoard of locusts by attacking the 

 chitinous insect exoskeleton or control nema- 

 todes that destroy the roots of crop plants (CAB 

 1993). Although strains of fungi can degrade 

 plastics and break down hazardous wastes such 

 as dioxin (Jong and Edwards 1 99 1 ), only a frac- 

 tion of these fungi have been screened as bene- 

 ficial organisms. 



