380 



SCIENTIFIC AND APPLIED PHARMACOGNOSY 



ciples, are probably erroneous. Power, Pharm. Jour., 1903, p. 183; 

 1907, p. 126. 



BURSERACE^E, OR MYRRH FAMILY 



Mostly tropical shrubs and trees, having alternate compound 

 leaves, and small flowers formed in racemes. The plants are espe- 

 cially distinguished by their internal secretory system. Schizo- 

 lysigenous balsam canals or gum-resinous canals (Fig. 167) occur 



...It 



FIG. 167. Transverse section of the bark of one of the Burseraceae, probably 

 Commiphora Myrrha: P, bark made up of sclerotic cells (si) and cork (d); 

 o, more or less spheroidal secretion canals, one of which (O) shows the irregular 

 spreading of the gum-resin; m, medullary rays; b, bast fibers; k, crystals 

 of calcium oxalate; p, parenchyma. After Vogl. 



within the sclerenchymatous pericycle, also in the secondary cortex 

 and medullary rays and occasionally in the primary cortex and pith. 

 The epidermal layer in the leaves is usually modified to mucilage. 

 The pericycle is a composite and continuous ring of sclerenchyma. 

 The trachese as a rule have simple perforations, which are very large 

 in the walls adjoining the parenchyma cells. Wood fibers also have 

 simple pores, being occasionally septate. The medullary rays are, 



