120 BOTANY. 



.'estivation ; tube sometimes witli scales, alternate with the lobes of the 

 limb. Stamens five, inserted in the base of the corolla, and alternate with 

 its lobes. Disk annular, hypogynous. Ovary free, two- to four-celled, rare- 

 ly by abortion one-celled ; ovules definite, erect, when more than one, col- 

 lateral ; style one, usually bifid, rarely two ; stigmas obtuse or acute. Fruit 

 succulent or capsular, one- to four-celled, with septifragal and scpticidal, or 

 circumscissilo dehiscence. Seeds albuminous ; embryo curved or spiral ; 

 cotyledons corrugated or inconspicuous ; radicle inferior. Herbs or shrubs, 

 usually twining, sometimes parasitical, often with a milky juice, and with 

 alternate, undivided, or lobed, exstipulate leaves, rarely leafless. They occur 

 chiefly in tropical and temperate regions. The order has been divided into 

 two sub-orders. 



Sub-order 1. Convolvulece, true Bindweeds, leafy plants with the corolline 

 tube not scaly, embryo curved, cotyledons conspicuous. 



Sub-order 2. Cuscutea, Dodders, leafless parasites, having scales on the 

 corolline tube, embrj'O spiral nnd filiform, cotyledons inconspicuous. There 

 are forty-five genera and upwards of TOO species. Examples : Cal^'stegia, Con- 

 volvulus, Ipomcea, Exogonium, Dichondra, Cuscuta. 



This order contains plants of considerable economical importance. Jalap is 

 obtained from Exogonium purga (Convolvulus jalapa) a native of Mexico ; 

 Convolvulus scammonia yields scannnony. The root of Batatas edulis (Con- 

 volvulus batatas) is known as the sweet potatoe. 



Exogonium purga, Jalap plant, Mexico {pi. Q^.ßg'. 7) ; «, pistil ; b, capsule ; 

 c, a seed. 



Order 92. IIvdropii yllace.*:, the Water-leaf Family. Herbs, commonly 

 hair3% with mostly alternate and cut-lobed leaves, regular five-merous, and five- 

 andr(jus flowers, as in the Borage Family, but the ovary ovoid and entire, one- 

 celled, with two parietal few- or many-ovuled placentas, which usually project 

 into the coll, und often line it like an interior pod. Style two-cleft above. 

 Bod globular, two-valved, few-seeded. Seeds reticulated or pitted, amphitro- 

 pous, with a minute embryo in cartilaginous albumen. Flowers chiefly blue or 

 white, in one-sided cymes or racemes, which are coiled from the apex when 

 young ; pedicels bractless. Examples : Hydrophyllum, Phacelia, Eutoca. 

 All North American. 



Order 93. Diapensiaceve, Mountain-box Family. Dwarf and tufted, 

 somewhat shrubby plants (only two in number), with small and evergreen 

 heath-like foliage, the fruit agreeing with Polcmoniaceae, as do the flowers, 

 except in the folloAving points, viz. Calyx of five separate and strongly 

 imbricated persistent sepals, like the bracts. Stamens five, inserted in the 

 very sinuses of the bell-shaped corolla ; filaments short and flat ; anthers 

 opening transversely across the cells on the inside. Style single, stigma 

 minutely three-lobed. Examples : Diapensia and Pyxidanthera, both low, 

 evergreen shrubs. Diapensia lapponica is found in the Alpine summits of 

 Mounts Washington, and Marcy or Tahawus. 



Order 94. Polemoniace.^, the Phlox Family. Calyx inferior, five-divided, 

 persistent, sometimes irregular. Corolla regular, rarely irregular, five-lobed. 

 Stamens five, inserted on the middle of the tube of the corolla, and alternate 

 120 



