On these plantations, rubber trees are cultivated just the same as other crops. All weeds are removed and great care is used with the young trees. Low-growing plants which absorb nitrogen from the air which enriches the soil, such as the passion flower and other sensitive plants, were planted around these small rubber trees, for it was found that when the weeds were removed to give the trees a chance to grow, the ground became hard and dry. [Illustration: _Courtesy of the United States Rubber Co._] The method of tapping is different, too. Instead of ten to thirty taps, a series of cuts the shape of a V is made on four sides of the tree, from the bottom up to as high as a man can reach, and a cup placed at the point of the V. Another way is to make one long cut down the tree and then cut out slanting channels about one foot apart into this, and put a cup at the bottom of the long cut; another is making a spiral around the tree with the cup at the bottom. How is Rubber Cured on Modern Plantations? With these big plantations some other way to cure the rubber had to be devised from the smoking process used in curing the native rubber which comes from South America. The milky juice is emptied from the cups into a tank and lime juice is added and it is then allowed to stand. The juice, as it comes from the tree, contains considerable water: the lime juice is added to separate the rubber from the water. [Illustration: A YOUNG RUBBER PLANTATION _Courtesy of the United States Rubber Co._] Sometimes separators are used much like our cream separators; in fact, the whole process and the appearance of the interior of these rubber “dairies” very much resembles our own dairies where real milk is made into butter, curds or cheese. Para, at the mouth of the Amazon, and Manaos, a thousand miles up, are both modern cities of more than one hundred thousand population. They have schools, churches, parks, gardens and museums, and, except for the Indians, certain peculiarities in architecture and the ever-present odor of rubber, they differ but little from our northern cities of equal size. Here the rubber markets are located and here the rubber is carefully examined, graded, boxed and shipped to New York or Liverpool. Plantation rubber usually comes in the form of sheets of various shapes and sizes. The rubber shown here is in oblong sheets. Sometimes it is in the form of “pancakes” or in “blocks.” Often, after being coagulated, it is smoked, and “smoked plantation sheet” is, next to Para, the best rubber obtainable. [Illustration: _Courtesy of the United States Rubber Co._] How is Crude Rubber Received Here?