696 A TEXT-BOOK OF BOTANY. 



of the spurious spigelia which has been on the market for some 

 years past. 



Ruellia ciliosa is a perennial herb which is distinguished from 

 the other species of the genus Ruellia by the leaves, stems, and 

 calyx being distinctly pubescent. The leaves are ovate-lanceolate, 

 nearly sessile and entire ; the flowers are blue, sessile, solitary, or 

 two or three in a cluster, in the axils of the leaves ; the stamens 

 are 4, and exserted. The fruit is an oblong, terete capsule con- 

 taining from 6 to 20 orbicular seeds. The plant is found from 

 New Jersey and Pennsylvania to Michigan and as far south as 

 Florida and Louisiana. Long cystoliths are found in some of the 

 epidermal cells of both surfaces of the leaf. 



Quite a number of the plants of the Acanthaceae are used in 

 the Tropics in medicine. One of these, Adhatoda Vasica of trop- 

 ical Asia, contains the alkaloid vasicine, and is said to have the 

 property of destroying algse which grow in the rice swamps. 



k. PLANTAGINACE^E OR PLANTAIN FAMILY. The 

 plants are annual or perennial herbs, represented by but few 

 genera, but numerous species. The principal genus is Plantago, 

 which includes 200 species that are widely distributed. Several 

 species of Plantago are used in medicine. The common plantain 

 (Plantago major) contains a glucoside, acubin ; emulsin ; and 

 invertin, and the short rhizome, considerable starch. The seed- 

 coat has an outer mucilaginous layer, and the mucilage of the 

 seeds of Plantago Psyllium, P. arenaria (both of Europe), and 

 P. Ispaghula (of the East Indies)' is used as a sizing material. 

 The seeds of a number of the species of Plantago are used as 

 bird food, particularly for canaries. 



/. OROBANCHACE^ OR BROOM-RAPE FAMILY. 

 This very interesting family is made up of plants which are 

 parasitic upon the roots of other plants and are consequently 

 rather light in color, as they develop no chlorophyll. Squaw-root 

 or Cancer-root (Conopholis americana) has the flowers arranged 

 in the form of a spike looking like an elongated cone, especially 

 after the flowers have begun to turn brown (Fig. 385). Another 

 little plant, also more or less white or yellow in color, is Beech- 

 drops (Epifagus), which develops upon the roots of the beech. 



