In general, spores and spore-bearing structures are preferably measured in water mounts, because published descriptions of these features have usually included dimensions determined from material mounted in water. The recorded characters are then utilized in tracing through analytical keys of the fungi to the several classes, orders, families, and genera, and finally to a species.

There are several standard keys in general use that lead to families and genera. G. W. Martin's key to families in the very useful Dictionary of the Fungi (third edition, 1950), by G. C. Ainsworth and G. R. Bisby, is a simplified and modern presentation, but for keys to genera one is forced to seek elsewhere. The keys to be found in E. A. Bessey's Morphology and Taxonomy of the Fungi ' (1950) are valuable for teaching purposes, but lead to representative genera only. The key to The Genera of Fungi (1931), by F. E. Clements and C. L. Shear, and those to be found in Engler and Prantl's Naturlichen Pflanzenfamilien (1897-1900), although today somewhat outmoded, are still essential references.

When a decision is reached as to the genus to which the fungus under consideration belongs, the problem remains of finding suitable literature bearing specific descriptions. The Guide to the Literature of the Fungi, the last chapter in Bessey's book, lists the more useful monographs and compendia as references. Yet one cannot depend upon compendia and monographs alone. They are out of date as soon as printed. It is therefore necessary to take account of the numerous increments constantly being published hence the need for access to well-cataloged library facilities.

Host indexes as short cuts are legitimate aids in quickly finding specific names that might apply. A pathogen may, of course, have thus far escaped record as upon the particular host, but it is likely to be recorded, if at all, on some related host. A. B. Seymour's Host Index (1929), based upon a complete but unpublished catalog of records up to 1924 and partly through 1926, is supplemented by the later detailed cumulative Index of Plant Diseases in the United States (1950) by F. Weiss and (1952, 1953) by F. Weiss and M. J. O'Brien. Various foreign lists of fungi and plant diseases, notably the anonymous List of Common British Plant Diseases (University Press, Cambridge, 1944) and the Enumeratio Fungorum (1919-1924), by C. A. J. A. Oudemans, are useful because most fungi tend to be cosmopolitan.

Actually, host indexes, like regional lists, are merely suggestions in determining identities, and one must ultimately depend on monographs, supplemented by the comparisons with herbarium specimens, including cited fungi exsiccati. Fungi exsiccati are standard replicate herbarium specimens of definite reference value, but comparisons with authentic specimens and with types constitutes a court of last resort.

Considerable information on taxonomic techniques with fungi is to be found in G. R. Bisby's Introduction to the Taxonomy and Nomenclature of the Fungi (1945) and in M. Langeron's Precis de Mycologie (1945). Whether a fungus in culture is an exact replicate of a species with ample record of pathogenicity can of course be determined only by means of culture studies with inoculation experiments in order to reveal comparable growth reactions and host symptoms.

When the identity of the fungus seems assured, there is still the question whether its name is acceptable. Even if a specific name (epithet) has been found entirely applicable to the specimen at hand that is, its features agree in all details with those noted in the description and it very closely resembles the type and other specimens regarded as authentic there is always the likelihood that there may be other names (synonyms) that might apply equally well. If one or more names are found to be synonyms, a decision must be made as to which is the correct one to use, according to the current International Code of Botanical Nomenclature (1952). Each of the several synonyms may be valid that is, it has been properly published; but conformity with the Code will determine which combination of generic and specific names is legitimate and, therefore, the proper choice. The present Code epitomizes the evolution in the nomenclature of fungi that began with the pioneer work of the eighteenth century.

Some persons, even specialists themselves, at times assume that the most expeditious way to get specimens or cultures identified is to refer them to individuals in other institutions. If the recipient is both competent and obliging, he is soon so overburdened with requests, many of them trivial but time consuming, that his own effectiveness in service and research is vitiated. Actually, the number of experienced mycologists equipped with laboratory, catalogs, and library facilities adequate for this kind of service in the United States, or in any other country for that matter, is limited to a few persons in a few institutions.

The taxonomist's concern, as well as his experience, is generally limited to particular genera or families. He naturally welcomes specimens and cultures that apply to his specialty; for him they are relatively easy to determine or else they challenge his mettle. Of course, no taxonomist can avoid a certain amount of drudgery; yet he should not be expected to determine the many common pathogens that ought to be more familiar to the senders. Some fairly common pathogens are often less familiar to the mycologist and can pose for him as much of a problem as any other unknown fungus. The sender is morally obligated to explain the significance and importance of his request, to supply the specimen or culture in good condition and in ample amount, as well as to accompany it with all pertinent data: Substrate, locality, date, etc. Since specimens and even cultures too often include more than one organism always possible as later contaminants, the sender should send microscopic preparations and sketches, sometimes even photographs, to avoid any possible confusion. Obviously, any materials entrusted to the mails should be so prepared that on receipt they will be in good order and not an unrecognizable mass mixed with broken glass.

As Bisby has remarked, "it is a matter of professional etiquette not to send parts of the same collection [or duplicate cultures] to be named by different experts" to which may be added, "unless the different experts are so notified." It is almost universally considered unethical for one to publish without acknowledgment a determination provided by another. It is furthermore a convention that, lacking special agreement to the contrary, any specimens sent to another for determination become the property of the recipient for deposit in the herbarium where he is employed and that he has the right to publish at his own discretion the result of his researches upon such materials.

WILLIAM W. DIEHL is a mycologist in the division of mycology and disease survey at the Plant Industry Station, Beltsville, Md. He has served the Department of Agriculture in Washington and at Beltsville since 1917. He is a graduate of Miami University and holds advanced degrees from Iowa State College and Harvard University.