CONVOLVULACE^E. 473 



beneath pubescent, on long petioles ; peduncles pilose, 1 — 3-flowered ; sepals ovate-rounded, 

 pubescent ; seeds covered with a long, silky down. 



Choisy, Convol. rar. 125; Linn. (Convolvulus), Sp. PI. i. 860; Pursh 

 (Ipomcea), Flor. i. 146 ; Michaux, Fl. Bar. Am. i. 141 ; Nuttall (I. mecho- 

 acana), Sill. Jour. 1822 ; Elliott (C. macrorhizus), Sketches, i. 252. 



Description. — Root perennial, somewhat fusiform, very large, weighing, when old, from 

 forty to fifty pounds, white, farinaceous. Stem twining, slightly angled, pubescent. Leaves 

 when young, acute, and tomentose beneath ; when old, often obtuse, and slightly muri- 

 cate ; petioles one to two inches long. Peduncles long, one to three-flowered. Calyx 

 pubescent. Corolla large, limb obscurely ten-lobed, externally pubescent, white, tinged 

 with purple. Filaments unequal, as long as the tube of the corolla, villous, and purple at 

 base. Style as long as the stamens, with a bilobate stigma. Capsule 2 — 3-celled. Seeds 

 dark brown, clothed with long, silky, brown hairs. The whole plant abounds in a lactes- 

 cent juice. 



This plant is a native of Mexico, and the southern parts of the United States, 

 and is the species supposed by Linnaeus to furnish the officinal Jalap, and 

 sent by Michaux to the Botanic Garden in Paris, under the name of Ipomea 

 macrorhiza, which was figured by Desfontaines (Ann. du. Mus. ii.), as af- 

 fording the purgative root; this opinion was also held by Pursh, who calls it 

 Ipomcea jalapa; it is also C. mechoacana of several botanists, but as is 

 now satisfactorily shown, does not furnish the jalap of commerce, nor do its 

 properties agree with those attributed to the mechoacan, under which name 

 it is highly probable that several species of the Convolvulaceae are confounded. 

 According to Dr. Baldwin (Elliott, Sketches, 1. a), it has no cathartic effect, 

 nor was any resin found in it on analysis ; he further states that it contains 

 much saccharine and farinaceous matter, and probably is not more cathartic 

 than the sweet potato. Yet it is said by De Candolle that it is purgative, and 

 in the Flor. Med. des Antilles, it is stated that it affords a white resin, which 

 is too powerful to be used. Under the name of Mechoacan, the earlier writers 

 clearly included all purgative roots coming from America, and at all re- 

 sembling Jalap, and to add to the confusion, it is said by many writers that 

 Linnaeus had described a species of Convolvulus under that name ; Mr. Nuttall 

 observes (Amer. Dispens. 374), " of which I have not been able to obtain any 

 account, being omitted in all the editions of the Species Plantarum, to which 

 I have had access." The fact is, Linnaeus made no such species, but in his 

 Materia Medica he says, " Convolvulus americanus, Mechoacana dicta, fyc." 

 The first to give this name was Vitman. 



What is called Mechoacan by Guibourl, is the product of C. mechoacan, 

 which is considered by De Candolle to be the same as the I. macrorhiza 

 of Michaux, is a root from South America, in variously shaped pieces, 

 deprived of its epidermis, white and farinaceous within, having no odour, 

 and a slightly acrid taste, and is slightly purgative. Although this article 

 is not now used, it was deemed deserving of notice, on account of its having 

 been mistaken for jalap. 



Another species of this genus is of far more interest, as forming an im- 

 portant article of food, — this is the B. edulis, or Sweet Potato, originally a 

 native of the East Indies, but now so extensively cultivated in the West 

 Indies and this country. The root of B. panicidatus is cathartic, and is 

 employed medicinally in India. 



Ipomea. — Linn. 



Calyx 5 sepals. Corolla campanulate. Stamens included. Style 1. Stigma capitate, 

 often bilobate. Ovary bilocular ; cells with 2 ovules. Capsule 2-celled. 



