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Lan Shi (Indigo Fruit), originally growing in the plains and marshes of Henei, is now found everywhere. People often cultivate it in vegetable gardens by making ridges; seedlings emerge in March and April, reaching a height of about two or three chi; leaves resemble those of *Polygonum hydropiper* (Shuiliao, Water Smartweed); flowers are red and white; fruits are similar to those of smartweed but larger, and black. The fruits are harvested in May and June.

According to records, there are several types of Indigo plants: one is *Indigofera tinctoria* (Mulan, Tree Indigo), produced in Lingnan, which is not used in medicine; another is *Isatis indigotica* (Songlan, Isatis Root/Leaf), which can be used to produce indigo dye, also known as Malan (Horse Indigo), referred to in *Erya* as "Qian, Malan"; a third type is *Persicaria tinctoria* (Liaolan, Polygonum Indigo), which can only be used for dyeing green-blue colors and cannot be used to make indigo paste; this is the variety commonly used in medical prescriptions. Additionally, there is a type of Malan in Fuzhou that is available year-round, with leaves resembling *Ixeris chinensis* (Kuyicai, Chinese Ixeris). Locals harvest it including the roots, dry it by baking, pound it into powder, and sieve it. Administered orally with wine in an amount equivalent to a coin-sized scoop, it is highly effective for treating blood stasis in women. Another variety is Wulan (Wu Indigo) from Jiangning, which sprouts in February and March, resembling mugwort (*Artemisia argyi*), with green leaves and white flowers. It has a cold nature, clears heat, detoxifies, and stops hematemesis. Although these two varieties differ in morphology, both bear the name "Lan" (Indigo).

Furthermore, in Chenliu, locals make a living planting indigo for dyeing deep blue fabrics. Fields of indigo stretch as far as the eye can see, preventing the cultivation of millet. To this day, indigo cultivation near the capital is particularly prosperous. It is said that indigo juice treats insect bites. Liu Yuxi recorded this method in *Chuanxin Fang*: Take one large bowl of indigo juice, add realgar (Xionghuang) and musk (Shexiang), grind them finely according to the required dosage, and mix into the indigo juice. Apply topically to the bite site. If it is a venomous bite, ingest the mixture thoroughly; the effect is extremely miraculous.

Previously, Yuanwai Zhang Jian served as a judge under Zhang Yanshang in Jiannan. He was suddenly bitten on the neck by a spotted spider. Overnight, two red lines appeared at the bite site, thin as chopsticks, encircling the neck and extending from the chest down to the heart region. After two nights, his head and face swelled and became painful, swelling to the size of several sheng bowls, and his abdomen gradually swelled, nearly leading to death. Zhang Yanshang, who greatly valued Zhang Jian, offered five hundred thousand cash from his own wealth, plus several hundred thousand from Zhang Jian's family, to recruit anyone who could cure him. Suddenly, a man responded to the call, claiming he could treat it. Zhang Yanshang initially doubted him and wanted to verify the prescription, so he ordered the medicine to be prepared on the spot. The man said, "I do not spare the prescription; I only wish to save lives." He then took a large porcelain bowl of indigo juice and threw the spider into it. After a long while, the spider emerged from the juice, appearing very lethargic and unable to move. He then pounded fresh indigo juice, added musk powder, and threw the spider in again, until the spider died. He then took more indigo juice and musk, mixed in realgar, and threw another spider into the mixture, which immediately dissolved into water. Zhang Yanshang and the others were amazed by this, so they had the man apply the preparation to the bite site. Within two days, the wound completely healed. Only a small scab formed at the bite site and fell off, leaving the skin restored.

Additionally, under the entry for Qingdai (Indigo Naturalis) in the middle-grade herbs, it is recorded that Qingdai came from Hu countries, and indigo pastes produced in Taiyuan, Luling, Nankang, etc., for dyeing, can also be applied externally to treat heat-toxic conditions. The foam floating on the surface of the dye vat, if purple-green in color, has the same efficacy as Qingdai.