There is distinctive chemistry within the family Theaceae. Sometimes, single crystals of calcium oxalate are present in Theaceous plants. Ellagic acid and common polyphenols including flavonols, flavones and proanthocyanins are widely distributed throughout the family. Gallic acid and catechins only occur in "Camellia" sect. "Thea (C. sinensis, C. taliensis" and "C. irrawadiensis".) Caffeine and its precursors theobromine and theophylline are only found in sect. "Thea" and are not found in other species of "Camellia" or other Theaceae. Caffeine content in the tea bush makes up 2.5-4% of the leaf's dry weight, and this high content of catechins and caffeine in the tea bush is the result of artificial selection by humans for these characters. Triterpenes and their glycosides (saponins) are found widely throughout the family in the seeds, leaves, wood and bark. Plants in this family are also known to accumulate aluminum and fluoride. The best known genus is "Camellia", which includes the plant whose leaves are used to produce tea ("Camellia sinensis"). In parts of Asia, other species are used as a beverage, including "C. taliensis, C. grandibractiata, C. kwangsiensis, C. gymnogyna, C. crassicolumna, C. tachangensis, C. ptilophylla", and "C. irrawadiensis". Several species are grown widely as ornamentals for their flowers and handsome foliage.