Coffee is very frequently adulterated, especially ground coffee. It is stated that the beans have been adulterated with artificial beans made of starch or of clay. It is not uncommon to find pebbles which have been added to increase the weight. Most commonly the beans are not carefully hulled and sorted so that a considerable percentage of spoiled beans and hulls are present. The coffee plant seems to be quite susceptible to the attacks of various pests. The coffee blight is a microscopic fungus (Hemileia vastatrix) very common in Ceylon which has on several occasions almost entirely destroyed the coffee plantations. The coffee borer is the larva of a coleopter (Xylotrechus quadripes) which injures and destroys the trees by boring into the wood. The pest is most abundant in India, while another borer (Areocerus coffeoa) is common in South Africa. Another destructive pest is the so-called coffee bug (Lecanium coffeoe).

Ground coffee is adulterated with a great variety of substances. The roasted and ground roots of chicory (Cichorium intybus), carrot (Daucus carota), beet (Beta vulgaris), are very much used. The rush nut (Cyperus esculentus), and peanut are also used. A large number of seeds are used for adulterating purposes, as corn, barley, oats, wheat, rye, and other cereals; further, yellow flag, gray pea, milk vetch, astragalus, hibiscus, holly, Spanish broom, acorns, chestnuts, lupin, peas, haricots, horse bean, sun flower, seeds of gooseberry and grape. The seeds of Cassia occidentalis known as "wild coffee" are used as a substitute for coffee in Dominica and are said to have a flavor equal to that of true coffee. Sacca or Sultan coffee consists of the husks of the coffee berry, usually mixed with coffee and said to improve its flavor. In Sumatra an infusion is made of the coffee leaves or the young twigs and leaves. This is said to produce a refreshing drink having the taste and aroma of a mixture of coffee and tea. Efforts have been made, especially in England, to introduce leaf coffee with but little success.

As already stated, most of the many varieties of coffee upon the market are obtained from one species, and are usually classified according to the countries from which they are shipped. The following are the most important varieties:

I. African, or Ethiopian Coffee.

1. Abyssinia.
2. Galla.
3. Kaffa.

1. Bohuri,
2. Sakki.
3. Salabi.

1. Java.
2. Batavia.
3. Tscheribon.
4. Samarang.
5. Menado of the Celebes.
6. Dadep of the Celebes.
7. Sumatra.

1. Manila.
2. Cavita.
3. Laguna.
4. Batanges.
5. Mindanao.

1. Nilgeri.
2. Madras.
3. Ceylon.
     a. Native.
     b. Plantation.