312 SYSTEMATIC BOTANY. 



CONVOLVULACE.E. THE BINDWEED OEDEE. 

 Coh. Convorvulales, Benth. et Hook. 



Diagnosis. Chiefly twining or trailing herbs, sometimes leafless 

 and parasitic, or shrubby and erect, often with some milky juice ; 

 with alternate leaves (or scales) ; -p. ,-,, 

 flowers regular, 5-androus ; calyx of 



5 imbricated sepals, the 5-plaited or ^P^C|l8i^ Fi 419 

 5-lobed corolla convolute or twisted in l ' 



the bud; ovary 2-celled (rarely 3- 

 celled), or with 2 separate pistils, with 

 2 erect ovules in each cell, the cell 

 sometimes doubled by a false partition 

 between the seeds, thus falsely 4-celled ; 

 embryo lirge, curved or coiled in mu- 

 cilagii ous perisperm, with foliaceous 

 cotyledons, or (Cuscutece) filiform and F % l 1 L5 nel ~ 8haped C r Ua ** 

 coiled with the cotyledons scarcely per- FIR. 412. Plicate aestivation of the 

 ceptible ; radicle inferior. Illustrative 

 Genera : Convolvulus, L. ; Cuscuta, Tournef . 



Affinities, &c. This Order approaches the regular sympetalous Boragi- 

 nacese, Polemoniaceee, and allied Orders; the structure of the ovary 

 separates it from the first, the curved embryo and the fruits from the 

 second. Cordias also differ in their aperispermic seeds and superior 

 radicle. Some of the Convolvulacese are of shrubby habit, and depart 

 widely from the appearance with which we are most familiar. Cuscuta 

 is sometimes made the type of a distinct Order ; but the parasitical habit 

 is not a sufficient character. 



Distribution. A large Order, of which a few species occur in temperate 

 climates, but the majority belong to the tropics. 



Qualities and Uses. A purgative property generally characterizes these 

 plants, among which are several yielding important medicinal substances. 

 True Jalap is the root of Exoyonium Purya, Scammony of Convolvulus 

 Scammonia ; Pharbitis cathartica and Ipomosa tuberosa yield a similar 

 substance. The white hedge-Convolvulus (Ccdystegia sepiuni) has a 

 similar action, as also various Ipomcea and Convol'vuli, the active matter 

 being a kind of resin existing in the milky juice. The seeds of Pharbitis 

 Nil (semen Kaladanse) and P. c&rulea are also used as purgatives. On 

 the other hand, Ipomosa edulis forms a large fleshy tuber, which is widely 

 cultivated and eaten under the name of the Sweet Potato, and Ipomcea 

 macrorhiza has edible farinaceous roots. The twining and trailing plants 

 of this Order are mostly remarkable for the beauty of their flowers, and 

 many of them are cultivated; the garden Major Convolvulus is Pharbitis 

 purpurea, the blue Minor Convolvulus is Convolvulus tricolor. Convolvulus 

 arvensiSj Bindweed, grows everywhere, on the ground, rooting- at the 

 nodes ; C. SoldaneUa grows in like manner on the sea-shore ; Catystegia 



