Amino acid
Amino acids are organic compounds containing amine (-NH) and carboxyl (-COOH) functional groups, along with a side chain (R group) specific to each amino acid. The key elements of an amino acid are carbon (C), hydrogen (H), oxygen (O), and nitrogen (N), although other elements are found in the side chains of certain amino acids. About 500 naturally occurring amino acids are known (though only 20 appear in the genetic code) and can be classified in many ways. They can be classified according to the core structural functional groups' locations as alpha- (α-), beta- (β-), gamma- (γ-) or delta- (δ-) amino acids; other categories relate to polarity, pH level, and side chain group type (aliphatic, acyclic, aromatic, containing hydroxyl or sulfur, etc.). In the form of proteins, amino acid residues form the second-largest component (water is the largest) of human muscles and other tissues. Beyond their role as residues in proteins, amino acids participate in a number of processes such as neurotransmitter transport and biosynthesis.
Nanfang Caomu Zhuang
Li (1979: 119) notes that the "Yiwu Zhi" (quoted in the "Qimin yaoshu") may possibly be the original source for this "Nanfang caomu zhuang" entry: "the orange tree has white flowers and reddish fruits, which have fragrant peels and also sweet taste. It is produced in Kiangnan and not elsewhere". The "Taiping Yulan" quotes this same passage followed by an additional sentence: "There is an orange grove in Chiao-chih, where an administrative officer is installed, with a salary of 300 "shih" (picul) [of rice], who is responsible for presenting an annual tribute of oranges to the royal court."
The Kan is a kind of orange with an exceptionally sweet and delicious taste. There are yellow and red kinds. The red ones are called Hu-kan 壺柑 (jar orange). In the market, the natives of Chiao-chih sell ants stored in bags of rush mats. The nests are like thin silk. The bags are all attached to twigs and leaves, which, with the ants inside the nests, are for sale. The ants are reddish-yellow in color, bigger than ordinary ants. In the south, if the Kan trees do not have this kind of ant, the fruits will all be damaged by many harmful insects and not a single fruit will be perfect. There are now two trees of Kan in the Hua-lin Garden. When in fruit, the Emperor has the court entourage wine and dine by their side and the fruits are picked and given to all. (63, tr. Li 1979: 118-119) 
"Húgān" (壺柑) is now called "pènggān" (椪柑 "Citrus poonensis", ponkan, Chinese honey orange"). Ma (1978: 243-244) says the first few sentences appear Zhou Chu's (236-297) "Fengtuji" (風土記 "Record of Local Conditions"), which is the likely source for this "Nanfang caomu zhuang" entry. Both Duan Chengshi's (9th century) "Yuyang zalu" (酉陽雜俎) and the (early 10th century) Lingbiao luyi (嶺表錄異) retell the citrus ant story.