Nostoc is actually a kind of algae. According to the "National Directory of Chinese Herbal Medicines" and "China's Traditional Chinese Medicine Resources", the variety name of Nostoc is 'Nostoc algae'. It is named because its shape and color after drying resemble those of scalp. , born in arid grassland areas, has the function of sand fixation. In order to reduce the spread of desertification in the northwest region, the mainland has banned the collection, sale and export of nostoc in recent years.

To determine the authenticity of Nostoc, you can conduct microscopic analysis or chemical testing. Use a microscope to analyze Nostoc. Under a high-power microscope, you can see the beads-like cells in Nostoc, but there are no beads-like cells in the non-Nostoc parts.

As for chemically identifying whether Nostoc is mixed with starch, you can first soak a small amount of Nostoc in a cup of boiling water for a period of time, then disperse the soaked Nostoc in a transparent and light-transmitting place, and add the number Drop the iodine solution until each Nostoc root is stained and wait for two to three minutes; the real Nostoc will be green, but in the sample mixed with non-Nostoc, the non-Nostoc part will appear obviously dark blue or black due to iodine and starch substances. A chemical reaction occurs that causes the originally starchy portion of non-vegetables to appear dark blue or black. But if the vegetable part does not contain starch, this method is not suitable.

Nostoc is produced in Gansu, Shaanxi, Qinghai, Xinjiang, Ningxia and Inner Mongolia. According to mainland data, in Inner Mongolia alone, more than 100,000 foreigners flock to Inner Mongolia every year. Nostoc and licorice have caused very serious damage to the grassland ecological environment, with the damage area reaching more than 200 million acres.