C. Ritchie Bell

Variation and Classification

The key to social evolution, cultural progress, and scientific advancement is communication; and the basis of effective communication is classification and the resulting nomenclature. Language itself would not be possible without classification: every noun (a class of word!) represents a kind, or class, of object; every verb (another class of word!) represents a kind or class of action. Indeed, it appears that the biological evolution of man is related to the evolution of speech and the selective increase in size of that portion of the brain which functions in communication. Since everyone who thinks, speaks, or writes must also classify, the basic concepts involved in classification and identification are a fundamental and functional part of every person’s thought and communication process.

Sources of Variation

Because of the open pattern of plant growth, a primary, and often misleading, source of variation is the phenotypic variability of many genotypes. If the range of phenotypic expression of a genotype is large, or, as stated in the previous chapter, if the primary control of the phenotype is environmental, a single plant, or plants of a single genotype, may vary considerably under different environments. The resulting variation pattern may be similar to a variation pattern that is primarily under genetic control. For example, a plant may have a tall form and a dwarf form; however, possession of the “tall” genotype does not in itself insure that the plant actually will fulfill its genetic potential and produce a tall phenotype. Some environmental factors or a combination of factors—such as moisture, temperature, soil nutrients, light—might be so inadequate as to limit the growth of this potentially tall plant and, therefore, we might get a dwarf plant that will be morphologically similar to a genetically dwarfed plant. The difference would be that the genetic dwarf, when self-pollinated, would probably breed true and produce only dwarf offspring regardless of the environment, whereas seed from the environmental dwarf could, under better growing conditions, produce the appropriate ratio of tall plants.

Manual of the Vascular Flora of the Carolinas

This illustrated manual describes and discusses the unusually rich and varied flora of the Carolinas, from the semi-tropical coast of South Carolina to the northern forests of the high North Carolina mountains. The manual treats in detail and in a concise format more than 3, 200 species of trees, shrubs, vines, herbs and ferns that grow without cultivation in this two-state area. Special features include diagnostic illustrations, keys for identification, detailed descriptions, flowering and fruiting dates, habitat data, distribution data, and pertinent synonymy for each species. County dot maps show the distribution of each species if found in more than five counties throughout the two-state area, and general ranges beyond our borders are given in the text. First published in 1968, Manual of the Vascular Flora of the Carolinas is an established reference for professionals, students, and plant enthusiasts throughout the Southeastern United States. It is based on the collection and examination of more than 200,000 live specimens. Many of these specimens are now housed in the herbarium at the University of North Carolina at Chapel Hill

Nomenclature and Keys

Throughout history, as man has needed to communicate about specific plants, he has given each such plant a common name. These common names were usually applied only to local plants of medicinal, religious, or economic importance, but the name given was seldom based on any actual botanical characteristics. They were neither applied in a systematic way, nor was there any conscious attempt to use the names to indicate relationship between plants. Therefore, the common name for a particular plant often varied, and still does, from one locality to another; or conversely, a particular common name might apply to several different plants in different areas. “Buttercup,” for example, might refer to a member of the genus Ranunculus or to a member of the unrelated genus Narcissus.

Correlation, Evaluation, and Presentation of Taxonomic Data

Both classification and identification depend upon a certain degree of character correlation and also upon discontinuity in the correlation patterns. Plant identification usually requires the use of only a few of a plant’s more obvious morphological characteristics, and only one or two characteristics are usually considered at any one time as the plant is worked through the key. In plant classification, on the other hand, it is necessary to consider and to evaluate all the pertinent information more or less simultaneously. Up to a point, an experienced taxonomist who has studied his material thoroughly can do this. Experience with a group of plants tends to develop a subconscious “feel” for the entities involved and for their interrelationships, and often this highly subjective evaluation is the basis for taxonomic opinion. So far all plants (and animals) have been classified by this method. This is not to say that the method is perfect or even that it is the best that can be devised. Indeed, as more aspects of biology are brought to bear on problems of relationship it is necessary to devise new ways of presenting larger numbers of variation patterns in such a way that they can be evaluated simultaneously and more objectively. Such methods not only help the taxonomist in his evaluations, but are of tremendous value in showing others how the taxonomist arrived at his conclusions.