Sugar cane is the source of sugar in all tropical and subtropical countries of the world. Estimates for 1966 and 1967 indicate world production of cane sugar was between 40 and 41 million tons. Production in the United States, excluding Puerto Rico, averaged 2,550,000 tons during those years - from 592,000 acres of cane in Hawaii, Florida and Louisiana. Sugar production in Puerto Rico averaged 850,000 tons for the two years. Several species of Saccharum are found in Southeast Asia and neighboring islands, and from these cultivated cane probably originated. The sweet juice and crystallized sugar were known in China and India some 2500 years ago. Sugar cane reached the Mediterranean countries in the eighth century A.D., and reached the Americas in early colonial times. The cane plant is a coarse growing member of the grass family with juice or sap high in sugar content. It is tender to cold, the tops being killed by temperatures a little below freezing. In continental United States, where freezing may occur during the winter, it is mainly planted in late summer or early fall and harvested a year later. In tropical countries it may be planted at almost any time of the year since the plant does not have a rest period. The season of active growth in continental United States is 7 to 8 months while in tropical countries growth is near continuous until harvest. This results in heavier yields of cane and sugar under tropical conditions. For example, yields of cane and sugar per acre in Hawaii, where the cane is grown for about 2 years before harvesting, are from 3 to 4 times vields in Louisiana and Florida from one season's growth. Sugar cane plants are propagated by planting sections of the stem. The mature stems may vary from 4 to 12 feet or more ill height, and in commercial varieties are from 0.75 to 2 inches in diameter. The stem has joints or nodes as in other grasses. These range from 4 to 10 inches apart along the above-ground section of the stem. At each node a broad leaf rises which consists of a sheaf or base and the leaf blade. The sheaf is attached to the stem at the node and at that point entirely surrounds the stem with edges overlapping. The sheath from one node encircles the stem up to the next node above and may overlap the base of the leaf on the next higher node. The leaf blade is very long and narrow, varying in width from 1 to 3 inches and up to 5 feet or more in length. Also, at each node along the stem is a bud, protected under the leaf sheath. When stem sections are planted by laying them horizontally and covering with soil a new stem grows from the bud, and roots grow from the base of the new stem. The stem branches below ground so several may rise as a clump from the growth of the bud at a node. In planting cane fields, mature cane stalks are cut into sections and laid horizontally in furrows. In continental United States sections with several nodes are laid while in tropical countries sections with 2 or 3 nodes are commonly used - since temperatures for growth are more favorable. Usually only one node on a stem piece develops. a new plant because of polarity along the stem piece.