White myrtle (Asclepiadaceae, Asclepiaceae, Asclepidium). 

Bai Wei, alias: Weicao, Zhiwei old, old melon ladle root, mountain smoke root, Baidang grass, white horse Wei, Baiqian, old gentleman's beard, Latin name: Cynanchum atratum Bunge. Asclepiadaceae, goose velvet rattan is an erect perennial herb, the root is like, has the aroma. Leaves ovoid or ovoid-oblong, apex acuminate or acute, base rounded, white tomentose on both surfaces, especially dense on leaf back and veins; Cymes umbrella-shaped, without total pedicels, born around stems, flowers dark purple, calyx outside tomentose, Corolla spoke, outside pubescent, ciliate; lobes peltate, rounded, as long as column, apex of anther with 1 round diaphragm; Oblong inflated; stigmas flattened. Follicles solitary, acuminate to tip, base obtuse, middle dilated, seeds flattened; seed hairs white, flowering from April to August, fruit from June to August. The root and part of the rhizome are used for medicine, have the effect of removing deficiency, clearing heat and dispersing swelling, generating muscle and relieving pain, and can treat postpartum deficiency, vomiting, urine leaching, nephritis, urinary tract infection, edema, bronchitis and rheumatic low back and leg pain. 

Morphological characteristics. 

Erect perennial herbs, up to 50 cm tall; roots whisker-shaped, fragrant. Leaves ovoid or ovoid-oblong, 5 × 8 cm long, 3 × 4 cm wide, apex acuminate or acute, base rounded, white tomentose on both surfaces, especially dense on leaf back and veins; lateral veins 6 to 7 pairs. Cymes umbrella-shaped, sessile, with 8-10 flowers around stems; flowers dark purple, ca. 10 mm in diam.; calyx tomentose outside, with 5 small glands on inner base; Corolla spoke, pubescent outside, ciliate; Corona 5-lobed, lobes peltate, rounded, as long as column, anther tip with 1 round diaphragm; pollen block 1 per locule, pendulous, oblong dilated; stigmas flattened. Follicles solitary, acuminate to tip, base obtuse, middle dilated, 9 cm long, 5 × 10 mm in diam.; seeds flattened; seed hairs white, ca. 3 cm long. The flowering period is from April to August, and the fruit stage is from June to August. 

Growth habit. 

Suitable for grass, grassy slope, arid land, arid wasteland, scrub, coastal beach, river, forest edge roadside, forest meadow, valley stream forest, hillside meadow, hillside meadow, In the open forest and by the stream on the hillside, It is suitable for a mild and humid climate. The sandy loam or loam with good drainage, fertile, deep soil layer and rich humus is suitable. Grow in 100 to 1800 meters above sea level of the river, dry wasteland and grass, mountain ditches, forest grassland is common. 

Geographical distribution. 

It is distributed in most parts of the country and is born in mountainous areas. Produced in Heilongjiang, Jilin, Liaoning, Shandong, Hebei, Henan, Shaanxi, Shanxi, Sichuan, Guizhou, Yunnan, Guangxi, Guangdong, Hunan, Hubei, Fujian, Jiangxi, Jiangsu and other provinces and regions; It is distributed from the northwest of Yunnan to the northeast, through Shaanxi and Hebei to Heilongjiang, to the north of the Tropic of Cancer in the south and to the coastal provinces in the east. North Korea and Japan, too. Type specimens were collected near Beijing. 

Pharmacological action. 

Baiwei oil can directly strengthen myocardial contraction and has the effect of detoxification and diuresis. The effect on the heart is that the myocardial contractile effect can be enhanced and the heart rate can be slowed down, which can be used in the treatment of congestive heart failure. Antibacterial effect of this product also has an inhibitory effect on pneumococci. 

Treatment of hemiplegia: Baiwei 15g, Zelan 10g, pangolin 6g, fried in water. 3 cases were treated with satisfactory results. ("Guangdong traditional Chinese Medicine"). 

Treatment of vascular inhibitory syncope: Baiwei 30g, Codonopsis 15g, Angelica 15g, roasted licorice 6g, water decoction. 11 cases were treated, 9 cases were cured, all of them were effective. (Journal of Integrated traditional Chinese and Western Medicine). 

Adverse reactions: 

Baiwei has a strong cardiotonic effect, overdose, has caused cardiotonic glycoside-like poisoning reaction, the toxic dose is 30 to 45g, palpitation, nausea, vomiting, dizziness, headache, diarrhea, salivation and other poisoning symptoms, clinical medication should be paid attention to.