By its configuration, Porto Rico is divided into two parts very distinct from each other in almost every respect and of primary importance in all the affairs of the island. The north side, which comprises about two-thirds of the total area, is kept constantly wet with almost daily rains. On the south it has been known not to rain for a whole year in some places. On the north side grows an abundance of luxuriant, tropical vegetation; on the south in many localities are barren hills covered only with scrub brush. But throughout the island there is great local variation in all the climatic and physical conditions. Along most of the north side there stretches a low, coast plain, out of which rise numberless, small, steep hills. This plain, everywhere well watered, is in most places very fertile, but in the vicinity of Vega Baja it becomes a sandy waste. This sand desert is one of the most peculiar places it has ever been my fortune to visit. There is no grass (turf-making grass is almost unknown in the tropics), neither are there large trees. Everywhere are low bushes not much more than ten feet tall. The sand beneath them is bare in many places, but is covered in others with various forms of herbage, most of which, instead of being composed of desert forms, as would be expected, is made up of the most typical water-loving plants, among which, Sphagnum (two species) and Utricularia are noteworthy. Imagine, if you can, a sphagnum bog shading into loose sand in a distance of only ten feet with no change in level. The explanation of this peculiar fact is, however, not hard to find. The rainfall is so copious that wherever there is any means of holding it, the hydrophytes take hold and spread, themselves acting as water holders when once started, while in other places the water quickly soaks into the sand and leaves it as dry as ever.