Plants and animals have evolved to fill all available habitats and ecological niches. Plants inhabit every possible environment including water, air, soil (wet and/or dry), other plants and also animals.
Green plants contain the organic pigment chlorophyll. When provided with light, carbon dioxide, water, and essential minerals they produce carbohydrates through a chemical process called photosynthesis mediated by the pigment chlorophyll. The light energy is converted into the chemical bond energy of a food molecule. The carbohydrate food molecules are utilized by the plant for cellular energy and as the basis for producing other molecules which are essential for the plant's growth and development. Usually the minerals and water are taken up by the root system and conveyed throughout the plant, including the sites of photosynthetic activity.
Plants have evolved to utilize all available habitats such as arid and semi-arid regions, moist and waterlogged areas, full sunlight to complete shade, from tropical to Arctic climates. Thus, it would be logical to expect that plants would evolve to survive in nutrient-poor soils and/or water.
The evolution of carnivorous plants is speculative due to the paucity of the fossil record. Flowering plants (angiosperms) began to evolve during the Cretaceous period of the Mesozoic Era. The flowering carnivorous plants, the topic of this book, therefore, cannot be older than 136 million years. The oldest carnivorous plant fossil is Aldrovanda pollen found in rock of the Eocene period that began 53 million years ago and ended 37 million years ago. The earliest Droseraceae pollen is found in the Miocene period, 26 to 12 million years ago.
Many plants today are adapted to foliar feeding. That is, when a nutrient (fertilizer) solution is sprayed on the leaves, the plant can absorb the nutrients through the leaves into the plant body. The beginning of carnivory could have taken place when some leaves formed shallow depressions in which rain water was retained for a period of time after a rain shower. These leaves would be ideal water reservoirs for insects. In the process of obtaining a drink, some insects would drown and eventually be decomposed by bacteria living in the water. The nutrients released into the water could have been absorbed by the leaf into the plant body. This process, similar to foliar feeding, would provide a distinct advantage to plants growing in nutrient-poor soils barely able to provide sufficient nutrients for growth. It would have provided them with a distinct survival advantage. The deeper the depression in the leaf, the more insects could be drowned and decomposed. In times of stress or overcrowding the plants that could derive nutrients through their leaves would be better able to compete in nutrient-poor soil. The plants able to obtain additional nutrients from their leaves would be stronger and healthier and more likely to produce offspring. As time passed, those plants that evolved more effective traps, means of attracting insects and directional guides—that is, the arrangement of nectar-producing glands and hairs that lead the prey into the trap— would be better able to survive in nutrient-poor soils.
The characteristics that distinguish carnivorous plants—such as visual and odiferous lures, directional guides, secreting glands, absorbing glands, trapping, and rapid movement—are found in various plants not considered carnivorous. Some non-carnivorous plants trap insects to effect pollination. Plants such as Mimosa -pudica and the Telegraph plants (Desmodium) have leaves that exhibit rapid motion. Some tree leaves secrete a sticky substance that falls to the ground. While all of the individual characteristics of carnivorous plants can be found in other plants, when they are all combined in the same plant the organism is truly unique, a carnivorous plant whose modified leaves can trap and digest prey lured to the plant. The digested materials are utilized by the plant for its growth and development. The fascination with carnivorous plants partly stems from the ability of these plants to reverse the order we expect to find in nature. Carnivorous plants are the predators rather than the passive prey.
Common names used for plants usually are descriptive but confusing because the same plant may be called by different names in different geographic areas. One common name used for carnivorous plants, Fly Catcher, can refer, for example, to a member of the genus Sarracenia or the genus Dionaea. Another disadvantage of using common names is that they are not easily recognizable by people speaking other languages. In addition, plants from widely separated genera may have the same common name; common names may suggest relationships that do not exist; and there is no international body for governing common names. To remedy these problems a Latinized binomial system was adopted about a century ago. For the reasons noted in this paragraph binomial names are used in this book.
The binomial system had its beginnings in the sixteenth century and was used by the botanists Brunfels and Dodonaeus. Carolus Linnaeus, in the eighteenth century, standardized and popularized the binomial system, which was adopted in 1867 by the First Botanical International Congress in Paris. The system (International Code of Botanic Nomenclature) is under constant review, and changes are made when necessary. Even though the system is not perfect, it does provide only one name for each species of plant. No two plants can have the same genus and species name.
In the binomial system plant names are Latinized because at the time of its development, Latin was the universal language of scholars. The name consists of two words: the first word, the genus name, is capitalized; and the second word, the species name, is not. These terms often describe some characteristic of the plant. For example, Drosera, a genus name, is derived from a Greek word meaning dew and refers to the droplet of mucilage on the ends of the tentacles. In the binomial name, Drosera rotundifolia, the species name rotundifolia refers to the plant's round leaves. Genus and species names are italicized when in print and when written or typed, the binomial is underlined. In technical writing the binomial name is followed by the name or standard abbreviation of the person's name who officially described the plant. If there has been controversy over the plant and its name has been changed, there may be more than one person's name following the binomial name—for example, Sarracenia purpurea f. heterophylla (Eaton) Fernald. The names of individuals are not italicized.
A genus consists of a group of plants which have very similar characteristics. For example, the genus Felis includes all cats, which have many common features. In the cat population there are cats that are sufficiently different from the other cats to be subdivided into a smaller group; this is done with a species name. Thus, the household cat is Felis catus, while the tiger, another member of the cat family, is Felis tigris and the cougar is Felis concolor.
There are finer subdivisions than species. These are in order of decreasing distinction, along with their abbreviations in parentheses, as follows: subspecies (ssp.), form (f.), and variety (var. or v.).
The members of a species have many similar characteristics, but in some cases there are enough minor differences to divide the members into two or more groups called subspecies. An example is Sarracenia purpurea ssp. purpurea and Sarracenia purpurea ssp. venosa.
Within the population of Sarracenia purpurea ssp. purpurea there are members distinguished from the rest by the absence of red coloration. This group is a division of a subspecies and called a form. The correct name for the plants lacking red coloration is Sarracenia purpurea ssp. purpurea f. heterophylla. If there are some differences in the members of a form, they are designated as a variety.
Subdivisional names are italicized but the reference names or abbreviations are not. Either reference names or their abbreviations can be used. This is illustrated by the following examples, Sarracenia purpurea subspecies purpurea form heterophylla, or Sarracenia purpurea ssp. purpurea f. heterophylla.
Once the full name of a plant is used in a discussion and as long as the genus discussed is not changed, the genus name can be abbreviated in further references. For example, after the binomial Drosera binata is used once, its further use in the same document is written D. binata.
Even though one genus may be quite distinct from another there are groups of genera (plural of genus) which have enough similarities that they are grouped into families. This is illustrated in chart 1, where the 7 families and 15 genera of carnivorous plants are listed.
Hybrid plants are produced from two different species or hybrids. Hybrids may occur spontaneously in the wild as the result of natural agents carrying the pollen from the flower of one species to another. Or, hybrid crosses may be made by plant breeders.
Hybrids are identified by one or both of two names: the formula name, or the collective epithet. For example, the formula name of one Sarracenia hybrid is Sarracenia minor X Sarracenia psittacina. This formula indicates the parentage of the hybrid. In usual practice the female parent producing the seed is listed first in the formula name. If this information is unknown, then the parental species are listed alphabetically.
The collective epithet for all hybrid plants resulting from the cross between S. minor and S. psittacina is Sarracenia X formosa. The "X" before the second name indicates that the plant is a hybrid. When Sarracenia are under discussion, the formula name is often written S. minor X S. psittacina, and the collective epithet as S. X formosa.
The collective epithet may also be a word or a phrase of not more than three words in a modern language. The hybrid designation for the cross S. alata X S. psittacina, for example, is Sarracenia (Robin Louise). In this case the "X" is omitted and the collective epithet placed in parentheses following the genus name.
A hybrid which shows exemplary characteristics that distinguish it from the other hybrids of the same parentage may be designated as a cultivar. "Cultivar" is a term which indicates a plant created by man. The term was formed from the two words "cultivated" and "variety." It is used to denote a group of cultivated plants that are distinctive from other members of the same group (grex), whether it be a species, subspecies, variety, or a hybrid of plants in cultivation or in the wild. The difference between a cultivar and other members of the same group resides in such characteristics as color, shape of leaves, size, or floral configuration.
Cultivars may arise or be developed by hybridizing species or hybrids; selecting the best seedling of a self-pollinating cultivar; inbreeding; and propagating natural and/or induced mutations. A cultivar may be derived from cultivated plants or may be found in a natural population of plants. The cultivar must be propagated by seed if it is an annual; but if a perennial, vegetative means of propagation are used in order to maintain its distinguishing characteristics. Sometimes a characteristic that was distinctive in a plant is not heritable; that is, it does not show up in plants propagated from a selected plant. Such a plant cannot be considered a cultivar. In order for a plant to be the basis of a cultivar, its particular identifying traits must be named according to the rules codified in the International Code of Nomenclature for Cultivated Plants (latest edition, 1980). Such cultivars must have fancy names; that is, not a botanical name in Latin form. (But cultivar names published prior to 1959 may be botanical names in Latin form.) A cultivar from a hybrid is designated by adding a fancy name to the hybrid's collective epithet or the formula name. The fancy name is preceded by 'cv.' or is enclosed in single quotation marks. For example, if a plant from the cross S. alata X S. psittacina displayed inheritable vivid red blotches, it could be designated as the cultivar 'Red'. The proper name would be Sarracenia (Robin Louise) cv. Red, or (Sarracenia alata X S. psittacina) 'Red'.
Discretion should be exercised in the naming of new cultivars so that the distinctions are not based on minor or trivial differences.
To make new cultivar names legal or valid, the name and a description of the plant indicating its difference from other plants in the same group, along with the parentage and history and, if possible, a diagram or photograph, must be published and distributed to the public. Publication is accomplished by having it appear in a dated catalog, book, periodical, or by photocopy, ditto, or mimeograph, with distribution to a significant number of people.
The cultivar name should also be registered with the registration authority designated for the genus. The job of the registration authority is to catalog cultivar names and descriptions to prevent both duplication of names and the same cultivar being assigned more than one name. For example, suppose you develop a cultivar and decide to call it Sarracenia alata cv. Yellow Gem. You send the description of the plant, along with the name, to the registration authority. The registrar checks previous registrations to determine if the name has already been used by someone else, and also if the cultivar you "developed" has already been registered by someone else. If the former, you simply choose another fancy name and resubmit your application. If the latter, you have no choice but to drop your cultivar name and work on developing another cultivar.
Unfortunately, at this time there is no designated registration authority for carnivorous plants.
For additional information on cultivar naming and registration, consult the International Code of Nomenclature for Cultivated Plants—1980, which is in many libraries and available through the American Horticultural Society, Mt. Vernon, Virginia, 22121.
While the foregoing section may seem complicated and pedantic, it is the simplest and most accurate way to deal with plants.
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