THE BOTANY OF COFFEE
_Its complete classification by class, sub-class,
order, family, genus, and species—How Coffea
arabica grows, flowers, and bears—Other species and
hybrids._
The coffee tree, scientifically known as _Coffea arabica_, belongs
to the two-leaved class of a large sub-kingdom of vegetable plants
known as the _Angiospermæ_. Because it bears a flower arranged with
its corolla all in one piece, forming a tube-shaped arrangement, it is
further classified as _Sympetalæ_ or _Metachlamydeæ_, which means that
its petals are united.
Pursuing its classification still further, botanists place it in the
order _Rubiales_ and in the family _Rubiaceæ_ or madder family, which
also includes various herbs, and a few American plants, like the
familiar bluets or Quaker ladies, and partridge berries. Quinine and
ipecac are also members of this family.
Botany divides all families into smaller sections known as genera, and
the coffee plant belongs to the genus _Coffea_. Under this genus are
several sub-genera, and to the sub-genus _Eucoffea_ belongs the common
coffee, which the trade and the general public know best, _Coffea
arabica_.
_Coffea arabica_ is the original species indigenous to Abyssinia
and Arabia, and for many years it was known as “Java” when it came
from Java and “Mocha” when it came from Arabia. The _Arabica_
seed transplanted to different soils and climates takes on local
characteristics, and this gives us Bourbon, Mexican, Coban, Blue
Mountain, Bogota, Bourbon Santos, etc., as the case may be.
There are many other species of coffee besides _Arabica_. They haven’t
been described frequently, because, with one or two exceptions, they
are commercially unimportant. Indeed, all botanists do not agree in
their classification of the species and varieties of the _Coffea_
genus. The systematic division of this interesting genus is far from
finished; in fact, it may be said hardly to be begun.
_Coffea arabica_ we know best because of the important role it plays in
commerce.
_Complete Classification of Coffee_
Kingdom _Vegetable_
Sub-kingdom _Angiospermæ_
Class _Dicotyledoneae_
Sub-class _Sympetalæ or Metachlamydeæ_
Order _Rubiales_
Family _Rubiaceæ_
Genus _Coffea_
Sub-genus _Eucoffea_
Species _C. arabica_
The coffee plant most cultivated for its berries is, as already stated,
_Coffea arabica_, which is found in tropical regions, although it can
grow in temperate climates. Unlike most plants that grow best in the
Tropics, it can stand low temperatures. It requires shade when it grows
in hot, low-lying districts; but, when it grows on elevated land, it
thrives without such protection. There are about eight recognized
species of _Coffea_.
_Coffea arabica_ is a shrub with evergreen leaves, and reaches a
height of fourteen to twenty feet when fully grown. The shrub produces
branches of two forms, known as uprights and laterals. When young,
the plants have a main stem, the upright; which, however, eventually
sends out side shoots, the laterals. The laterals may send out other
laterals, known as secondary laterals, but no lateral can ever produce
an upright. The laterals are produced in pairs and are opposite, the
pairs being borne in whorls around the stem. The laterals are produced
only when the joint of the upright, to which they are attached, is
young; and, if they are broken off at that point, the upright has no
power to reproduce them. The upright can produce new uprights also;
but, if an upright is cut off, the laterals at that position tend
to thicken up. This is very desirable, as the laterals produce the
flowers, which seldom appear on the uprights. This fact is utilized in
pruning the coffee tree, the uprights being cut back, the laterals then
becoming more productive. Planters generally keep their trees pruned
down to six to twelve feet.
The leaves are lanceolate, or lance-shaped, being borne in pairs
opposite each other. They are three to six inches in length, thin, but
of firm texture. They are very dark green on the upper surface, but
much lighter underneath. The margin of the leaf is entire and wavy. In
some tropical countries, the natives brew a coffee tea from the leaves
of the coffee tree.
The coffee flowers are small, white, and very fragrant, having a
delicate characteristic odor. They are borne in the axils of the leaves
in clusters, and several crops are produced in one season, depending
on the conditions of heat and moisture that prevail in the particular
season. The different blossomings are classed as main blossoming and
smaller blossomings. In semi-dry, high districts, as in Costa Rica or
Guatemala, there is one blossoming season, about March, and flowers and
fruit are not found together, as a rule, on the trees; but in lowland
plantations, where rain is perennial, blooming and fruiting continue
practically all the year, and ripe fruits, green fruits, open flowers,
and flower buds are to be found at the same time on the same branchlet,
not mixed together, but in the order indicated.
The flowers are tubular, the tube of the corolla dividing into five
white segments. The number of petals is not at all constant, not even
for flowers of the same tree.
While the usual color of the coffee flower is white, the fresh stamens
and pistils may have a greenish tinge, and in some cultivated species
the corolla is pale pink.
The size and condition of the flowers are entirely dependent on the
weather. The flowers are sometimes very small, very fragrant, and
very numerous; while at other times, when the weather is not hot and
dry, they are very large, but not so numerous. Both these kinds “set
fruit,” as it is called; but at times, especially in a very dry season,
the trees bear flowers that are few in number, small, and imperfectly
formed, the petals frequently being green instead of white. These
flowers do not set fruit. The flowers that open on a dry sunny day show
a greater yield of fruit than those which open on a wet day, as the
first mentioned have a better chance of being pollinated by the insects
and the wind.
After the flowers droop, there appear what are commercially known as
coffee berries. Botanically speaking, “berry” is a misnomer. These
little fruits are not berries, such as are well represented by the
grape; but are drupes, which are better exemplified by the cherry and
the peach. In the course of six or seven months, these coffee drupes
develop into little red balls about the size of an ordinary cherry;
but, instead of being round, they are somewhat ellipsoidal, having
at the outer end a small umbilicus. The drupe of the coffee usually
has two locules, each containing a little “stone” (the seed and its
parchment covering), from which the coffee bean (seed) is obtained.
Actually, then, the coffee berry is not a berry but a “drupe”; also,
the coffee bean is not a “bean” but a seed.
Some few drupes contain three beans, while others, at the outer ends of
the branches, contain only one round bean, known as the peaberry. The
number of pickings corresponds to the different blossomings in the same
season; and one tree of the species _Arabica_ may yield from one to
twelve pounds a year.
In countries like India and Africa, the birds and monkeys eat the ripe
coffee berries. The so-called “monkey coffee” of India, according
to Arnold, is the undigested coffee beans that passed through the
alimentary canal of the animal.
The outer fleshy part or pulp surrounding the coffee beans is at
present of no commercial importance. From the human standpoint, the
pulp, or pericarp, as it is scientifically called, is rather an
annoyance, as it must be removed in order to procure the beans. This
is done in one of two ways. The first is known as the dry method, in
which the entire fruit is allowed to dry, and is then cracked open. The
second is called the wet method; the pericarp is removed by machine,
and two wet, slimy seed packets are obtained. These packets, which
look for all the world like seeds, are allowed to dry in such a way
that fermentation takes place. This rids them of all the slime; and,
after they are thoroughly dry, the endocarp, the so-called parchment
covering, is easily cracked open and removed. At the same time that the
parchment is removed, a thin silvery membrane, known scientifically as
the spermoderm (which means seed skin), referred to in the trade as the
silver skin, beneath the parchment, comes off too. There are always
small fragments of this silver skin to be found in the groove of the
coffee bean contained within the parchment packet.
We have said that the coffee tree yields from one to twelve pounds a
year, but of course this varies with the individual tree and also with
the region. In some countries the whole year’s yield is less than 200
pounds an acre, while there is on record a patch in Brazil which yields
about seventeen pounds a tree, bringing the acre yield much higher.
The beans do not retain their vitality for planting for any
considerable time; and, if they are thoroughly dried, or are kept for
longer than three or four months, they are useless for that purpose. It
takes the seed about six weeks to germinate and to appear above ground.
Trees raised from seed begin to blossom in about three years, but a
good crop cannot be expected of them for the first five or six years.
Their usefulness, save in exceptional cases, is ended in about thirty
years.
The coffee tree can be propagated other than by seeds. The upright
branches may be used as slips, which, after taking root, will produce
seed-bearing laterals. The laterals themselves cannot be used as slips.
In Central America, the natives sometimes use coffee uprights for
fences, and it is no uncommon sight to see the fence posts “growing.”
Thus far there are 12 recognized varieties of _Arabica_, as follows:
_Laurina_, _Murta_, _Menosperma_, _Mokka_, _Purpurescens_, _Variegata_,
_Amarella_, _Bullata_, _Angustifolia_, _Erecta_, _Maragogipe_, and
_Columnaris_.
Two other species of coffee that have become better known in the trade
are _Liberica_ and _Robusta_. _Liberica_ is a much larger and sturdier
tree than _Arabica_, and sometimes reaches a height of thirty feet.
Its leaves are twice as long, and the flowers are larger and borne in
dense clusters. At any time during the season, the same tree may bear
flowers, white or pinkish, and fragrant, or even green, together with
fruits, some green, some ripe and of a brilliant red. The corolla has
been known to have seven segments, though as a rule it has five. The
fruits are large, round, and dull red; the pulps are not juicy, and are
somewhat bitter. Unlike _Coffea arabica_, the ripened berries do not
fall from the trees, and so the picking may be delayed at the planter’s
convenience. The _Liberica_ bean produces a drink which is classed as
inferior to _Arabica_ by trade experts.
The _Robusta_ plant is larger than either _Arabica_ or _Liberica_.
The leaves of _Robusta_ are much thinner than those of _Liberica_,
though not so thin as those of _Arabica_. The tree, as a whole, is a
very hardy variety, and bears blossoms even when it is less than a
year old. It blossoms throughout the entire year, the flowers having
six-parted corollas. The berries are smaller than those of _Liberica_,
but are much thinner skinned; so that the coffee bean is actually not
any smaller. They mature in ten months. Although the plants bear as
early as the first year, the yield for the first two years is of no
account, but by the fourth year the crop is large. Recently cup tests
have established high merits in certain strains of _Robusta_. A variety
of _Robusta_ called _Canephora_ has flowers tinged with red, its
unripe berries are purple, and the bean narrower and more oblong than
_Robusta_. It grows well in high altitudes. Among the allied _Robusta_
species are _Ugandæ_ and _Quillou_.
Experiments in coffee culture are constantly being made by well-known
botanists, and some interesting hybrids have been produced, the most
popular belonging to a crossing of _Liberica_ and _Arabica_. _Excelsa_,
an allied _Liberica_ species, has also given much promise.
A species of coffee growing wild in the Comoro Islands and Madagascar
has been found practically caffein-free. Certain Porto Rico coffees are
also very low in caffein content.
[Illustration]
[Illustration: Green (Longitudinal Cross Section).]
[Illustration: Roasted (Tangential).
GREEN AND ROASTED BOGOTA COFFEE (MAGNIFIED 200 DIAMETERS)]