346 BOTANY AND PHARMACOGNOSY. 



branches, and leaves which are characterized by a number of layers 

 of water-containing cells. 'The plants grow in muddy swamps, 

 or along the sea-coast where the water is brackish, a number 

 together forming the so-called " Mangrove swamps." 



The root and bark of the Mangrove, as well as other species 

 of Rhizophora and several species of Bruguiera, contain a large 

 quantity of tannin which resembles catechu. The aerial roots of 

 Rhizophora are used by the natives of Polynesia in the making of 

 bows, and the woods of several genera are used in carpentry. 



g. MYRTACE^ OR MYRTLE FAMILY.— This is a group 

 chiefly of shrubs and trees, some, as of species of Eucalyptus, 

 being the loftiest trees known, attaining a height in some instances 

 of 105 M. The plants are indigenous to Australia and tropical 

 America and some are extensively cultivated. 



Eucalyptus species. — The leaves frequently vary in shape 

 and in arrangement on the young and older branches of the same 

 plant. On the young branches they may be, as in Eucalyptus 

 Globulus, ovate or broadly elliptical, opposite and sessile, while 

 on older branches they are scythe-shaped, pellucid-punctate, petio- 

 late and alternate (Fig. 258). In the latter case the petioles are 

 twisted and the leaves stand edgewise so that both surfaces are 

 equally exposed to the light and hence of similar structure. The 

 flowers are solitary, or in cymes or umbels, occurring in the axils 

 of the leaves. Petals are wanting and the whitish stamens, which 

 are numerous and inflexed in the bud, are covered by an oper- 

 culum or lid which is considered to be formed by the union of 

 the sepals, and which dehisces on the maturing of the stamens, 

 this being one of the most characteristic features of the genus. 

 The fruit is a 3- to 6-locular truncated capsule or pyxis. 



This is a very important genus from an economic point of 

 view, among the products being the volatile oil (oil of eucalyptus), 

 and eucalyptol, both of which are official, and the tannin or so- 

 called' " gum," known as Eucalyptus kino (p. 655). 



Jambosa Caryophyllus {Eugenia Caryophyllata). — This is a 

 small tree indigenous to the Molucca Islands and now extensively 

 cultivated in the Tropics. The leaves are opposite, ovate-lance- 

 olate, acuminate, petiolate, entire and evergreen. The flowers are 

 rose-colored and in cymes; the fruit is berry-like and constitutes 



