YAM ROOT 109 



the stems is interesting in that the fibrovascular bundles are collat- 

 eral and arranged in a manner similar to those found in dicotyledons. 

 In the rhizomes the fibrovascular bundles are of a collateral type but 

 are separated from each other as is usual in the monocotyledons. 



DIOSCOREA. Wild Yam Root, Colic Root or Rheumatism Root. 

 The rhizome of Dioscorea villosa (Fam. Dioscoreaceae), a perennial 

 herbaceous, twining plant, with beautiful cordate, 9- to 11-ribbed 

 leaves, small greenish-yellow flowers and triangular winged capsules. 

 The plant is common in the Eastern and Central United States and 

 is easily cultivated. The branching rhizomes with adhering roots 

 are gathered in the spring and fall, and dried. 



Description. Rhizome horizontal, woody, somewhat knotted 

 and compressed; the pieces usually not more than 5 cm. in length 

 and 12 mm. in thickness; externally light or yellowish-brown with 

 small circular stem-scars on the upper surface and with conical shaped 

 buds and slender wiry roots on the lateral portions; fracture short; 

 inodorous; taste somewhat acrid. 



Inner Structure. Epidermis thin-walled and provided with 

 large water pores. The starch-bearing cortical parenchyma is of 

 two kinds, that in the periphery being thin walled and is frequently 

 abraded in the drug, while the inner layers are thick-walled and 

 impart to the drug its hardness. There is no endodermis or pericycle 

 and the collateral vascular bundles are scattered throughout the 

 central parenchyma. Raphides of calcium oxalate are also present. 



Constituents. An acrid resin and a principle allied to saponin. 

 Continued boiling is said to impair the acrid properties of the drug. 



Literature. Holm, Merck's Report, 1913, p. 311. 



Yam Root. Yam is a popular name for several of the edible 

 species of Dioscorea and is sometimes incorrectly applied to certain 

 varieties of the sweet potato. The tubers of D. alata weigh as much 

 as 25 K. In the South Sea Islands they are eaten after boiling, which 

 destroys the acrid principle. The starch is also separated and is 

 sometimes marketed under the name of " South Sea Island Arrow- 

 root." The starch grains are mostly single, ellipsoidal or ovoid, 

 frequently bent and characterized by an excentral point of origin 

 of growth and numerous lamellse. 



AMARYLLIDACE^;, OR AMARYLLIS FAMILY 



A group of herbaceous plants mostly indigenous to tropical and 

 subtropical regions. It includes a number of genera, which are used 

 for ornamental purposes, as Amaryllis, Crinum, Galanthus (or snow 



