The coffee tree, scientifically known as Coffee arabica, is native to Abyssinia and Ethiopia, but grows well in Java, Sumatra, and other islands of the Dutch East Indies; in India, Arabia, equatorial Africa, the islands of the Pacific, in Mexico, Central and South America, and the West Indies. The plant belongs to the large sub-kingdom of plants known scientifically as the Angiosperms, or Angiosperm, which means that the plant reproduces by seeds which are enclosed in a box-like compartment, known as the ovary, at the base of the flower. The word Angiosperm is derived from two Greek words, sperma, a seed, and aggeion, pronounced angeion, a box, the box referred to being the ovary.
This large sub-kingdom is subdivided into two classes. The basis for this division is the number of leaves in the little plant which develops from the seed. The coffee plant, as it develops from the seed, has two little leaves, and therefore belongs to the class Dicotyledoneæ. This word dicotyledoneæ is made up of the two Greek words, di(s), two, and kotyledon, cavity or socket. It is not necessary to see the young plant that develops from the seed in order to know that it had two seed leaves; because the mature plant always shows certain characteristics that accompany this condition of the seed.
In every plant having two seed leaves, the mature leaves are netted-veined, which is a condition easily recognized even by the layman; also the parts of the flowers are in circles containing two or five parts, but never in threes or sixes. The stems of plants of this class always increase in thickness by means of a layer of cells known as a cambium, which is a tissue that continues to divide throughout its whole existence. The fact that this cambium divides as long as it lives, gives rise to a peculiar appearance in woody stems by which we can, on looking at the stem of a tree of this type when it has been sawed across, tell the age of the tree.
In the spring the cambium produces large open cells through which large quantities of sap can run; in the fall it produces very thick-walled cells, as there is not so much sap to be carried. Because these thin-walled open cells of one spring are next to the thick-walled cells of the last autumn, it is very easy to distinguish one year’s growth from the next; the marks so produced are called annual rings.
We have now classified coffee as far as the class; and so far we could go if we had only the leaves and stem of the coffee plant. In order to proceed farther, we must have the flowers of the plant, as botanical classification goes from this point on the basis of the flowers. The class Dicotyledon is separated into sub-classes according to whether the flower’s corolla (the showy part of the flower which ordinarily gives it its color) is all in one piece, or is divided into a number of parts. The coffee flower is arranged with its corolla all in one piece, forming a tube-shaped arrangement, and accordingly the coffee plant belongs to the sub-class Sympetalæ, or Metachlamydeæ, which means that its petals are united.
The Coffee Tree, Showing Details of Flowers and Fruit
The next step in classification is to place the plant in the proper division under the sub-class, which is the order. Plants are separated into orders according to their varied characteristics. The coffee plant belongs to an order known as Rubiales. These orders are again divided into families. Coffee is placed in the family Rubiaceæ, or Madder Family, in which we find herbs, shrubs or trees, represented by a few American plants, such as bluets, or Quaker ladies, small blue spring flowers, common to open meadows in northern United States; and partridge berries (Mitchella repens).
The Madder Family has more foreign representatives than native genera, among which are Coffee, Cinchona, and Ipecacuanha (Uragoga), all of which are of economic importance. The members of this family are noted for their action on the nervous system. Coffee, as is well known, contains an active principle known as caffein which acts as a stimulant to the nervous system and in small quantities is very beneficial. Cinchona supplies us with quinine, while Ipecacuanha produces ipecac, which is an emetic and purgative.
The families are divided into smaller sections known as genera, and to the genus Coffee belongs the coffee plant. Under this genus Coffee are several sub-genera, and to the sub-genus Eucoffea belongs our common coffee, Coffee arabica. Coffee arabica is the original or common Java coffee of commerce. The term “common” coffee may seem unnecessary, but there are many other species of coffee besides arabica. These species have not been described very frequently; because their native haunts are the tropics, and the tropics do not always offer favorable conditions for the study of their plants.
All botanists do not agree in their classification of the species and varieties of the coffee genus. M.E. de Wildman, curator of the royal botanical gardens at Brussels, in his Les Plantes Tropicales de Grande Culture, says the systematic division of this interesting genus is far from finished; in fact, it may be said hardly to be begun.