Carvalho says that the coffee plant needs sun, but that a few hours daily exposure is sufficient. Hilly ground has the advantage of offering the choice of a suitable exposure, as the sun shines on it for only a part of the day. Whether it is the early morning or the afternoon sun that enables the plant to attain its optimum conditions is a question of locality. [Illustration: CROSS SECTION OF MOUNTAIN SLOPE IN YEMEN, ARABIA, SHOWING COFFEE TERRACES These miniature plantations are found chiefly along the caravan route between Hodeida and Sanaa] [Illustration: CLEARING VIRGIN FOREST FOR A COFFEE ESTATE IN MEXICO] [Illustration: COFFEE NURSERY UNDER A BAMBOO ROOF IN COLOMBIA] [Illustration: THE FIRST STEPS IN COFFEE GROWING] In Mexico, Romero tells us, the highlands of Soconusco have the advantage that the sun does not shine on the trees during the whole of the day. On the higher slopes of the Cordilleras--from 2,500 feet above sea-level--clouds prevail during the summer season, when the sun is hottest, and are frequently present in the other seasons, after ten o'clock in the morning. These keep the trees from being exposed to the heat of the sun during the whole of the day. Perhaps to this circumstance is due the superior excellence of certain coffees grown in Mexico, Colombia, and Sumatra at an altitude of 3,000 feet to 4,000 feet above sea-level. Richard Spruce, the botanist, in his notes on South America, as quoted by Alfred Russel Wallace,[315] refers to "a zone of the equatorial Andes ranging between 4,000 and 6,000 feet altitude, where the best flavored coffee is grown." PROPAGATION. Coffee trees are grown most generally from seeds selected from trees of known productivity and longevity; although in some parts of the world propagation is done from shoots or cuttings. The seed method is most general, however, the seeds being either propagated in nursery beds, or planted at once in the spot where the mature tree is to stand. In the latter case--called planting at stake--four or five seeds are planted, much as corn is sown; and after germination, all but the strongest plant are removed. Where the nursery method is followed, the choicest land of the plantation is chosen for its site; and the seeds are planted in forcing beds, sometimes called cold-frames. When the plants are to be transplanted direct to the plantation, the seeds are generally sown six inches apart and in rows separated by the same distance, and are covered with only a slight sprinkling of earth. When the plants are to be transferred from the first bed to another, and then to the plantation, the seeds are sown more thickly; and the plants are "pricked" out as needed, and set out in another forcing bed.