390 



EXOGENOUS OR DICOTYLEDONOUS PLANTS. 



portant properties. Several exude a balsamic resin, such as Lada- 

 num from a Cistus of the Levant.* 



725. Ord, Hypericaceae (the St. John's-wort Family). Shrubs or 

 herbs, with a resinous or limpid juice, and opposite entire leaves, 

 destitute of stipules, and punctate with pellucid or blackish dots. 

 Flowers regular. Calyx of four or five persistent sepals, the two 

 exterior often smaller. Petals four or five, twisted in aestivation, 

 often with black dots. Stamens commonly polyadelphous and nu- 

 merous. Capsule with septicidal dehiscence, many-seeded. 

 Ex. Hypericum (St. John's- wort, Fig. 553) is the type of this 

 small family. The plants yield a resinous acid juice, and a bitter, 

 balsamic extractive matter.f Embryo straight ; albumen little or 



* ORD. BIXACE^E consists of tropical trees or shrubs, not resembling any 

 of the other orders with parietal placentae, and is here mentioned because 

 Bixa Orellana, of tropical America, yields the Arnotto of commerce; which 

 is the waxy, orange-red pulp that surrounds the seeds, and is separated from 

 them by washing. It is chiefly used for staining cheese, and in the prepara- 

 tion of chocolate. 



t ORD. GUTTIFER^E, or CLUSIACE^E, consisting of tropical trees, 

 with a yellow, resinous juice, large flowers, and thick and shining entire 

 leaves, is nearly allied to Hypericaceoe, and exhibits the acrid properties of the 

 latter family in a much higher degree. Gamboge is the hardened resinous 



FIG. 546. The Rock-Rose, Helianthemum Canadense. 547. Flower from which the petals 

 and stamens have fallen. 548. Magnified cross-section of the ovary ; with a single stamen, 

 showing its hypogynous insertion. 549. Cross-section of a capsule, loculicidally dehiscent ; 

 the seeds therefore borne on the middle of each valve. 550. An ovule. 551. Plan of the flower. 

 552. Section of a seed, showing the curved embryo. 



