Plant specimens collected in the 



field, often thousands of miles 



from Chicago, are carefully 



prepared and packed to ensure 



they will be suitable for mounting 



when they finally arrive at the 



Museum. 





^■l 



move small portions for detailed analysis. However, 

 the greatest use of these museum specimens is for 

 classification. 



For tht»e who classify plants and animals, the pri- 

 mary task is to develop sound concepts of the species, 

 often thought to be the basic building blocks of nature. 

 Species are generally defined as populations of plants or 

 animals that do not interbreed with other similar plants 

 or animals. While this is a fine conceptual basis for a 

 species definition, it is difficult to apply in practice. For 

 the vast majority of plant species, especially in the 

 tropics, we look for morphological discontinuities in 

 groups of related species. If two closely similar species 

 consistently differ in minor characteristics (and there 

 do not seem to be any intermediate specimens) we can 

 be quite confident that they are not interbreeding. It is 

 for this reason that the comparison of large suites of 

 specimens are essential for determining and defining 

 species correctly. Thus, the primary use of our speci- 

 mens is by taxonomists in their work of defining species 

 and understanding relationships. 



A question that often arises about our holdings is 

 whether we have more than one specimen of the same 

 species. The answer is that in the case of all but the 

 rarest species we do indeed have many specimens of the 

 same species. Collectors in the field have no way of 

 knowing what the Museum already holds, and they 

 may not kntiw the identity of many of the specimens 

 they collect. It is thus inevitable that many species are 

 represented by a suite of specimens, collected over 

 many decades and over a large area. The value of these 

 multiple collections is that they are central to dealing 

 with a wide variety of problems, from those of taxo- 

 nomic classification to those of biogeography and 

 ecology. Once a species is properly defined, large 



numbers of specimens will tell us over what geograph- 

 ical area the species occurs, in what kind of habitat it: 

 grows, when it flowers and fruits, how it varies over its 

 range, how people use it, and other bits of information. 



In effect, the herbarium is a "library" of dried 

 plants; and, as in the case of libraries, the larger the 

 number of specimens, the greater is the information 

 content. But there is a serious problem in our herbar- 

 ium: misidentified specimens can result in serious mis- 

 information. It is not uncommon for a misidentified 

 specimen to be found in a region or at an altitude where 

 the species whose name it carries has never been found 

 before. Misidentification is a common probem among 

 the plant collections for several reasons. For one thing, 

 higher plants number in the tens of thousands for most 

 continental areas. The sheer number of species invites 

 error and confusion. In addition, plants are highly vari- 

 able. Leaves can differ greatly on different plants of the 

 same species, or even in the same individual under 

 differing environmental conditions. Specimens with 

 flowers (and without fruit) can be difficult to correlate 

 with specimens of the same species with fruit (but lack- 

 ing flowers). Since a great many of our specimens come 

 from tropical areas where many species are still poorly 

 defined, our herbarium suffers from more than its share 

 of misplaced specimens. It is for this reason that we 

 welcome loan requests by researchers working on a par- 

 ticular group. We send about 25,000 specimens out on 

 loan each year and we trust that they will come back in 

 better order than when we sent them. 



Recently, the National Science Foundation in- 

 creased its support of our loan and curatorial activities, 

 helping us to continue serving the scientific commu- 

 nity. Our two millionth vascular plant is a small mile- 

 stone in a continuing responsibility. FM 



17 



