The custom has arisen of designating the kinds or species of plants by Latin-form names in two parts,—the first part or word standing for the genus or race-group, and the second part standing for the particular species or kind. Thus, all kinds of true clover belong to the genus Trifolium. The alsike clover is Trifolium hybridism; the white clover, T. repens; the common red clover, T. pratense ; the T. Alexandrinum. Varieties of species, or subordinate forms, are designated by a third Latin form word, as Trifolium pretense var. perenne, for the true perennial form of red clover. These names are always used with precision for one particular kind of plant, and they afford the only means of desig nating them accurately. Common or English names are of little service, as now used, in distinguishing species accurately.
Plants are also assembled in families, which are groups comprising genera that naturally resemble each other in certain bold or general characters. The farmer is specially concerned with the members of some of the family associations. The grass family, or Graminece, includes all the true grasses and the cereal grains, such as maize, wheat, oats, barley, rye, rice ; also, sorghum and sugar-cane. The rose family, Rosacece, contains many of the fruits,— all the stone-fruits and pome-fruits, raspberry, black berry, strawberry. The pulse family, Leguminosce, comprises the nitrogen-gatherers,—all peas, beans, clovers, vetches, alfalfa. The mustard family, Cruciferm, includes all the mustards, cabbages and kales, rape, turnip and rutabaga, radish. The nightshade family, Solanacem, includes potato, tomato, egg plant, pepper, tobacco. The rue family, or Rutacece, comprises all the citrons fruits, as orange, lemon, lime, kumquat, grape-fruit. Other families contain only one or two agricultural plants of commanding importance ; as cotton, of the Malvaccce or mallow family ; flax, of the Linaccce or flax family ; buck wheat, of the Polygonacere or knotweed family ; beets and mangels, of the Chenopodiacece or pigweed family ; sweet-potato, of the Convo/vu/acez or morning-glory family.
The number of distinct species of flowering plants now described is about 125,000. What this vast number has so far contributed to the food requirements of man has been made the subject of an inquiry by Sturtevant (Agricultural Science, iii, p. 174). Basing his list on Bentham and Hooker's "General Plan tarum" (1862-1883), in which about 110,000 species of flowering plants are recognized, in some 200 fam ilies and 8,349 genera, he arrives at the following figures : 4,233 species, belonging to 170 families and 1,353 genera, are known to have furnished food for man either habitually or during famine periods ; 1,070 species, belonging to 92 families and 401 genera, are or have been cultivated for human food. Among flowerless plants 431 species have been recorded as edible, but only 5 or 6 are cultivated. In other words, about 3; per cent of the known species of flowering plants furnish parts which can be eaten, and nearly 1 per cent are or have been cultivated for human food. About 300 species are cultivated to an impor tant or commercial extent.
De Candolle, in "Origin of Cultivated Plants," discusses the origins of 247 species which are "cultivated on a large scale by agriculturists, or in kitchen-gardens and orchards." These belong to 51 families. They may be tabulated as follows : Of C and F, 37 per cent are annuals, about S per cent biennials, 33 per cent herbaceous perennials, and about 22 per cent ligneous perennials.
Among all seed-bearing plants, "the annuals are not more than 50 per cent, and the biennials 1 or at most 2 per cent. It is clear that at the beginning of civilization plants which yield an immediate return are most prized. They offer, moreover, this advantage, that their cultivation
is easily diffused or increased, either because of the abundance of seed, or the same species may be grown in summer in the North, and in winter or all the year round in the tropics." Of the 247 species, 193 have been found wild, 27 half-wild or spontaneous and 27 are entirely unknown in a wild condition. Of the species in A and D, 63 per cent are known wild, and, of less than 2,000 years, 53 per cent.
Seven species (including the broad bean, tobacco, wheat and maize) appear to be extinct (or at least unknown) in a wild state.
The nativity of three ancient species of the group A is unknown—common bean (Phaseolus vulgaris) and two squashes (Cueurbita mosehata and C. ficifolia).
The very ancient species, group A, "are especially plants provided with roots, seeds, and fruits proper for the food of man. Afterwards come a few species having fruits agreeable to the taste, or textile, tinctorial, oil-producing plants, or yielding stimulating drinks by infusion or fermentation. There are among these only two green vegetables, and no fodder. The orders which predominate are the Crucifer, and Graminem." In De Candolle's discussion are not included several North American species that are now cultivated, as the native plums, cherries, raspberries, blackberries, and even the native grapes (on which a good part of our viticulture is founded). The addition of these would modify some of the above figures. For accounts of these plants, see Bailey's "Evolution of Our Native Fruits." The Standard Cyclopedia of Horticulture (1914-1917), the six-volume work founded on the earlier Cyclopedia of American Horticulture, accounts for 20,602 species of plants, offered by dealers and known in cultivation for food, ornament, fancy, medicine and other uses. In addition to these species, 6,715 recog nized Latin-named varieties are accounted for, making a total of 27,317 plants known to cultivation within the range of the Cyclopedia. The total number of binomial and trinomial botanical names admitted is 39,775, a good many of which, of course, are regarded as synonyms or duplicates. Of the more than 27,000 Latin-named species and varieties, 2,753 are native in North America north of Mexico. It is seen, therefore, that the western hemisphere is contributing great numbers of plants to domestication; if to this number are added the species derived from the hemisphere south of the Rio Grande, the contribution takes on great importance. Yet the species desirable for cultivation and known only in the wild are mom numerous than we appreciate.
Cultivated plants may be thrown into four broad classes : those grown for domestic animals ; those grown to provide shelter and clothing for man ; those that provide edible, condimental or medicinal parts or products for man ; those that appeal to the artistic impulses. These are not cultural groups however ; nor is it possible to make any consistent cultural classification, since all groups overlap. Perhaps we cannot do better, as a rough working classification, than to make the following somewhat indefinite associations : In the present volume it is proposed to consider in some detail the important field crops, excepting such as ordinarily fall under the department of horticulture. The leading medicinal crops are admitted for brief discussion, and many incidental plants are mentioned, in order to make the book useful for reference. It is the purpose of this Cyclopedia to catch the spirit of the main agricultural industries in North America.